| Boost controller | |
| Jon 86 745 MS | Team 745i.com now has the in cockpit boost controller available for shipping. Please contact us for more information and pictures. Jon Jacobs UPDATE 2/2006: Jon isn't making boost control units any more. However, owners interested in boost control products should visit the store at [url]http:\\scottiesharpe.com\store[/url] |
| Jon 86 745 MS | I have done quite a lot of experimentation with the new boost controller setup. I think the users will be quite happy with it. One thing is that by using the solenoid valve you definitly get boost much sooner than with out it. If you try just unhooking the wastegate hose you see boost start to come on at about 3000 rpm. With the controller you see boost begin at about 2500 rpm. There are times the the boost will come on much sooner. Say on a hill doing about 50 or 55 mph and then step on the gas. At this point the Motronic control system to the solenoid valve comes on and boost begins at less than 2000 rpm. The conteol knob is quite sensitive with the first opening and then is less so the more you open the valve. There are time that I bump 20 to 21 psi of boost but these are only for a second or so and only under certain conditions. Victor is the next user in line to get one. Let him tell you what he thinks. Oh Yea stomp on the gas with the valve off and when the boost starts to come on strong just open the valve all the way. It's like being shot out of a slingshot!!! HEHEHEHE. To much fun. |
| Bob745_Dallas | Sounds just like the Tuoma set-up. What you described is pretty much the way mine works. Two questions....when you hit that 20 psi what gear were you in and did you hear any knock at all? |
| Jon 86 745 MS | Yes very similar to Tuoma setup. As for peak boost hits around 20 psi it's only if I am around 45 to 50 mph and I step on the gas to make a down shift to second gear. It last maybe 1 or 2 seconds at most. John Stein told me he use to see the same thing with his 2.93 rear end. Now that he has the 3.91 he says he seldom see more that about 12 psi. As far as knocking goes I am running a 93 octane blend that puts my octane up close to 100. So far I have had no pinging. I never drive the car without the boost in octane. Jon Jacobs 86 745i (Das Rocket) 16 psi+ Boost with Team WWW.745i.com Performance Parts |
| Bob745_Dallas | Soumds just like mine and I have the 2.93 diff. still. I find that I can actually run the 20 psi in 3rd and 4th gears without knocking, but in the scenario you described where it comes on quick I will usually get a little pinging and the wastegate will open enough to bleed down the pressure. Mind you, I never run it at 20 psi for long. Sounds like you've merged Stein's theory with Matt Garrett's....extra fuel and higher octane. Are you using a regularly available octane booster? I've been tempted to add one myself. Matt mixes race gas with his, but he hangs out at the track. I don't really have a source, although I also haven't looked for it. I've done pretty well on the 93 so far, but it's starting to get hotter and I'm sure I'll need to do something to stay at the boosts levels I've been running the last few months. I've found that it hasn't been necessary to use the FMU during the cooler months (still installed but backed way off). Just changing the Motronic to a richer mixture setting has been enough, but we've already had a couple of 90+ degree days and the mixture has leaned out significantly. I'll be dialing her back in for hot weather shortly. |
| Jon 86 745 MS | Now that the temp is around 90 I put about 1/2 a bottle of Black 104+ Octane boost. I keep turning up the FMU pressure as the temp goes up. No pinging yet. I am running around 90 psi on the rail right now. If it starts to be a problem I will back off of the boost some. And yes if I kick down from forth to 3rd I can hit 20 psi. Like you I dont let it hang there. Jon Jacobs 86 745i (Das Rocket) 16 psi+ Boost with Team WWW.745i.com Performance Parts |
| Jon 86 745 MS | I have had several requests for this information. I have not personaly tried any of this but proably will soon. I am also looking for a blending chart form the Porsche Board. Hopefully thaey will give me the URL and I will post it. Rocket fuel FAQ Copyright ã 1999,2000 by Eliot Lim This paper may be freely distributed, provided it is distributed in its entirety Last revised: February 8, 2000 Background In late 1997 I became the lucky owner of 1 out of 150 1998 Porsche 993 Targas, the very last of the air cooled classics. As I drove it through the winter of 1997 and into the spring of 1998 I noticed that the engine lost some of its sweetness. Since this behavior was strongly related to ambient and engine temperature I suspected that the engine electronics were retarding its ignition timing due to insufficient fuel octane. I started experimenting with octane boosting by first adding small doses of over the counter octane boosters and noticed immediate improvement. The engine ran smoother and quieter, was more willing to rev and had noticeably sharper throttle response. The octane shortage was confirmed by the sticker on the filler cap that stated that 93 octane fuel was needed. Since the highest octane rated fuel that was commonly available in Washington state is 92, I decided to investigate long term cost effective octane boosting so that I could fully enjoy the performance that this car offered. My other car at the time, a 1990 Audi V8 quattro had an even more dramatic response to octane boosting. I managed to convince a few good friends to try it and the reaction was overwhelmingly positive. When I attempted a broader based dissemination of this exciting find, I was greeted largely by broad unyielding skepticism and plenty of FUD (fear, uncertainty, doubt) regarding toxicity, safety and engine damage. There arose a need to more clearly explain the details of octane boosting, hence giving rise to this article. Q: Will my car benefit from octane boosting? A: Consumer organizations have effectively emphasized the larger markups that oil companies charge for high octane gasoline, implying that for most vehicles higher octane fuel is a complete waste of money. It has been quite a long time since the consumer alert was issued. Since then engine technology has evolved greatly, while people's perceptions generally have not. Modern vehicles now use computerized engine management systems that can react to engine knock and retard ignition timing if low octane fuel is being used. Consequently cars are now being manufactured with very high compression ratios that appear to give good fuel economy and at the same time good performance. This combination does assume that fuel of adequate octane is being used. Q: Why bother to boost octane at all since my engine can run just fine on lower octane fuel? A: For a high compression engine to run on low octane fuel, the engine management system will need to retard the ignition timing to prevent preignition or pinging. Retarding the ignition timing means that the firing of the spark plug is delayed until a later moment in the compression stroke. It does not take much to see that a later onset of combustion means that the combustion is less complete, which in turn mean less power and poorer fuel economy. It is possible that the casual driver will still come out ahead in terms of saving money by using low octane fuel, but the retarded ignition advance also means a rougher running engine and a much duller throttle response. Thus octane boosting is not necessarily of interest to all motorists but rather the enthusiasts. For turbocharged or supercharged engines, insufficient octane will also lead the engine management system to curtail the amount of boost which in turn defeats the purpose of these engines. Q: How did you discover using toluene? A: Someone came across a web page that described various DIY home brew octane booster formulas. One of which used toluene as its main ingredient. As a Formula 1 racing fan of many years, I recalled that toluene was used extensively in the turbo era in the 1980s by all the Formula 1 teams. The 1.5 liter turbocharged engines ran as much as 5 bars of boost (73 psi) in qualifying and 4 bars (59 psi) in the actual race. Power output exceeded 1500bhp, which translates into 1000bhp/liter, an astronomical figure. A motorsports journalist, Ian Bamsey, was able to obtain Honda's cooperation for his book "McLaren Honda Turbo, a Technical Appraisal". The book documents the key role that the toluene fuel played in allowing these tiny engines to run so much turbo boost without detonation. The term "rocket fuel" originated from the Formula 1 fraternity as an affectionate nickname to describe its devastating potency. Thus I concluded that I should focus my research on using toluene for my octane boosting project. Individuals with good long term memory will recall that when unleaded gasoline was first introduced, only low octane grades were available. While it is not entirely clear that high octane super unleaded gas came about as a result of the advances in fuel technology in Formula 1, there is every reason to suspect that this is indeed the case, since many of the major oil companies were involved in the escalating race to develop increasingly potent racing fuel during this era. Q: Why do you think toluene is better than other types of octane boosters? A: Several reasons: Mindful of the evil reputation of octane boosters in general, toluene is a very safe choice because it is one of the main octane boosters used by oil companies in producing ordinary gasoline of all grades. Thus if toluene is indeed harmful to your engine as feared, your engine would have disintegrated long, long ago since ordinary pump gasoline can contain as much as 50% aromatic hydrocarbons. Toluene is a pure hydrocarbon (C7H8). i.e. it contains only hydrogen and carbon atoms. It belongs to a particular category of hydrocarbons called aromatic hydrocarbons. Complete combustion of toluene yields CO2 and H2O. This fact ensures that the entire emission control system such as the catalyst and oxygen sensor of your car is unaffected. There are no metallic compounds (lead, magnesium etc), no nitro compounds and no oxygen atoms in toluene. It is made up of exactly the same ingredients as ordinary gasoline. In fact it is one of the main ingredients of gasoline. Toluene has a RON octane rating of 121 and a MON rating of 107, leading to a (R+M)/2 rating of 114. (R+M)/2 is how ordinary fuels are rated in the US. Note that toluene has a sensitivity rating of 121-107=14. This compares favorably with alcohols which have sensitivities in the 20-30 range. The more sensitive a fuel is the more its performance degrades under load. Toluene's low sensitivity means that it is an excellent fuel for a heavily loaded engine. Toluene is denser than ordinary gasoline (0.87 g/mL vs. 0.72-0.74) and contains more energy per unit volume. Thus combustion of toluene leads to more energy being liberated and thus more power generated. This is in contrast to oxygenated octane boosters like ethanol or MTBE which contain less energy per unit volume compared to gasoline. The higher heating value of toluene also means that the exhaust gases contain more kinetic energy, which in turn means that there is more energy to drive turbocharger vanes. In practical terms this is experienced as a faster onset of turbo boost. Chevron's published composition of 100 octane aviation fuel shows that toluene comprises up to 14% alone and is the predominant aromatic hydrocarbon. Unfortunately composition specifications for automotive gasoline is harder to pin down due to constantly changing requirements. Chevron's web site also describes the problems of ethanol being used in gasoline. MTBE was heavily touted as a clean additive several years ago, and became a key ingredient in reformulated gasoline that is sold in California. But recently new studies arose that showed that MTBE was far more toxic than previously imagined. Organizations such as oxybusters have formed around the country to eliminate the use of MTBE in gasoline and several states, including California have passed new laws to eventually outlaw MTBE. Q: How much toluene should I use per tank of gas? A: Octane ratings can be very easily calculated by simple averaging. For example, the tank of an Audi A4 1.8TQ is 15.6 gallons. Filling it with 14.6 gallons of 92 octane and 1 gallon of toluene (114 octane) will yield a fuel mix of: (14.6 * 92) + (1 * 114) / 15.6 = 93.4 The Audi A4 1.8T is a good example of a car that has very high octane needs if it has been modified to produce more turbo boost. The base compression ratio of this car is a very high 9.5:1 and when an additional 1 bar (14.7 psi) of turbo boost is applied on top of it, the resulting effective compression ratio is way beyond what 92 or 93 octane fuel can ever hope to cope with. Most modified 1.8Ts running without octane enhancement are running with severely retarded ignition timing and boost. Q: Will toluene damage my engine or other parts of my car? A: A 5 or 10% increase in the aromatic content of gas will most likely be well within the refining specifications of gasoline defined by ASTM D4814, which specify an aromatic content of between 20% and 45%. What this means is that if the 92 octane gas that you started off with had an aromatic content of say 30% and you increased it by 10% to 40% you would still be left with a mix that meets the industry definition of gasoline. So the above question would amount to: "Will gasoline damage my engine or other parts of my car?" Even in the unlikely event that the 92 octane gas has a aromatic content of 45% the resulting mix would still be within the bounds of gasoline sold in other countries. Q: Isn't toluene an extremely toxic substance? A: The common perception of toluene's toxicity far exceeds reality. Fortunately there is an ample body of information available that specifically addresses this question. Toluene is more toxic than gasoline but it is certainly not agent orange or cyanide. US Environmental Protection Agency Chemical Summary US Agency for Toxic Substances and Disease Registry (ATSDR) National priority list of toxic substances Note that the ATSDR also rates gasoline as a hazardous substance. Mobil's spec sheet for toluene even goes as far as saying that "Based on available toxicological information, it has been determined that this product poses no significant health risk when used and handled properly." Q: Isn't toluene an active ingredient of TNT (trinitrotoluene) and is thus deadly? A: In the same way that cotton wool is the base ingredient of nitrocellulose (guncotton) which in turn is the main ingredient in modern smokeless gunpowder. Using this reasoning one could conclude that cotton wool is a deadly substance. This question reflects a poor understanding of basic chemistry but unfortunately it has been asked often enough. Q: How much does toluene cost, and where can I buy some? A: $10/gallon in a one gallon can at a hardware store, about $6/gallon in a 5 gallon can from a chemical supply or paint store, or $3/gallon in a 55 gallon drum from a chemical supply warehouse. Q: Can I just dump in 100% toluene into the tank like the F1 racers? vroom vroom vroom A: First of all, the F1 racers did not use 100% toluene, but 84%. The other 16% in their brew is n-heptane, which has an octane rating of zero. The reason for this strange combination is because the F1 rocket fuel was limited to the rules to being of 102 RON octane. The n-heptane is "filler" to make the fuel comply with the rules. Because toluene is such an effective anti knock fuel it also means that it is more difficult to ignite at low temperatures. The Formula 1 cars that ran on 84% toluene needed to have hot radiator air diverted to heat its fuel tank to 70C to assist its vaporization. Thus too strong a concentration of toluene will lead to poor cold start and running characteristics. I recommend that the concentration of toluene used to not exceed what the engine is capable of utilizing. i.e. Experiment with small increases in concentration until you can no longer detect an improvement. Q: Why not simply use racing gasoline or aviation fuel? A1: Most types of aviation fuel have very high lead content, which would rule out cars equipped with catalytic converters. Most piston engined aircraft burn leaded fuel. Also aviation fuel has a very different hydrocarbon mix to optimize volatility properties at high altitude. A2: Racing gasoline could be a much more convenient way to run high octane fuel compared to having to constantly mix in toluene with each fill up. There are, however a few caveats: You don't know for sure if you are really getting what is being advertised. You should find out if the fuel inspectors verify the actual octane of the racing gasoline in addition to ordinary gasoline. If you paid $3/gallon and only got 94 or 95 octane instead of 100 octane you may conclude erroneously that your car does not benefit from octane boosting. You don't know what octane boosters are used in the racing gasoline. The worst case scenario is buying leaded racing gasoline without knowing it. Unleaded racing gasoline may still contain damaging octane boosters like MMT or methanol. A very high alcohol content will lead to fuel line erosion, accelerated fuel pump wear, very poor fuel economy and possibly lower performance, as alcohols have a less impressive MON rating than aromatics. It takes smaller quantities of toluene to achieve the same octane boost compared to 100 octane racing gas. I have not seen unleaded racing gas for sale that exceeds the octane rating of toluene. Since toluene is not officially sold as a fuel, gas taxes do not apply. Also racing gasoline tend to have higher markups being of interest to the performance minded enthusiast and thus is very likely to be more expensive to buy and use long term than toluene, which is typically used in more mundane applications like paint thinner. Q: Ok, what is the catch? A: It should be mentioned that in the US, efforts are underway to reduce the aromatic content of gasolines in general as a higher aromatic content leads to higher benzene emissions. Benzene is an extremely toxic substance. However it should also be noted that the proportions that is being discussed in this FAQ is relatively small and in the grand scheme of things is probably insignificant. Moreover, the industrial standard for defining gasoline composition allows plenty of leeway in aromatic content and the proportions present in US gas is already lower than most other countries. I therefore feel that the information provided here is useful to a performance minded car enthusiast while not being significantly detrimental to the environment. Q: What safety measures can you recommend in handling toluene? A: The following is a good reference guide: Q: Do you have testimonies of others who have tried this? A: Some samples of feedback is reprinted with the names removed below. You may contact me if you wish to contact the respondents directly. -------------------------------------------------------------------------------- Since I didn't have any reference point for how much to use, I dumped about a half gallon of this mix into a mostly empty tank (the GT has a 16 gallon tank) and then filled up with Chevron 92 octane. I didn't get to drive the car until PIR the next morning, (my GF doesn't like the 200; it's too big) but the report was that there was no change for a mile or so, and then all of a sudden, the engine seemed to smooth out and became quite eager to rev and run. Well, by that calculation, I only managed to bump the octane to just shy of 93, but it seemed to make a big difference. I ran the car hard all day, (for reference, it's got an '87 MC turbo motor, K26, 12psi boost, and currently no intercooler) and even at 12 pounds of boost, I never once felt the ECU backing the timing off. Granted, the ambient temps never got above 50, and my water and oil temps were rock solid. (Oil just pushing above 100C) The only cars that I had to get out of the way for was an Integra Type R and a couple of race-prepped P-cars. I even managed to lap the NSX once! It was a really good day! <grin> -------------------------------------------------------------------------------- Okay, kids, gather round. This is important: we spend lots of money for our car, lot of money modifying and taking care of it, lots of effort and pride in owning it. So if someone comes along and proposes to give you something that would increase your enjoyment in driving by exponential measures and it would only cost you two or three bucks per tank of gas, would you be suspicious like the 100MPG carburetors? Would you listen long enough to real-life testimonies to consider this improvement for yourself? Well, this is the case for Toluene and what it can do for your V8Q if you been using anything less than 92+ octane. Get some.Try it. No harm, no risk. Use about 24-32 ounces per 1/2 to full tank. You will not look debonair. You will have to suspend your "cool" look. You may want to try this alone. YOU WILL HAVE THE SHITTEST, MOST PLASTER, GRIN ON YOUR FACE YOU HAVE EVER HAD! It won't come off. You'll tell the kids, daddy has his own "transformer". It will be like a new car...no, better than new! I took my family out to dinner tonight and could hardly keep from dropping it into manual and showing off like some teenager (I don't think my 17 year old daughter was inpressed). I wanna see some posts here with personal experiences by you guys using this stuff - I wanna know that my car is normal and hasn't been deprived ever since I've owned it. -------------------------------------------------------------------------------- I did the Rocket Fuel thing tonight on my Extremely Modified 5KCSTQ that runs 24 PSI of boost... And I can tell you not only does my ears and my butt say that the Rocket fuel is doing it's job but My ECU Data logger that gives me the timing value for all 5 cyls says it's working too. Before Rocket Fuel I was running full retard (14 Deg of timing) on boost and would still on occasion get some knock, now I'm getting timing numbers around 22 Deg's with ZERO knock ever. I'm running 2 Gallons of Toluene 7oz of ATF and 17.5 gals of 93 oct gas for a net octane of 95.15. I'm next going to try 3 Gallons of Toluene (96.23 Octane) to see what timing numbers I get. -------------------------------------------------------------------------------- After being convinced that my car was running below it potential - Owners manual recommends octane rating between 95 and 99, although it_will_run on octane as low as 91 - I stopped by Sherwin Williams and picked up a gallon. It was on sale for $5.85! Anyway, head to the chevron and pour a half gallon into the tank before pumping in the premium. The car took 16 gallons so there was still 4 gallons in the tank. I take off....nothing (obviously burning the fuel still in the lines). About 10 miles later, HOLY SH*****T!!!!!!!!!! It really does everything advertised by the list. It is so much more responsive from a stop and low speed, it really is impressive. I would agree with the sentiment that it feels like a totally different car. For the non believers, you really should try to get some higher octane fuel in your tank, whether through the use of Toluene or not. The owners manual recommends 95 to 99 octane** for optimal performance. With the half gallon of Toluene I added to the 92 octane, I was only running at approximately 92.6 octane and the difference was simply amazing! If you haven't tried it, do yourself a favor and give it a whirl - I swear you'll be impressed. (**note: this person confused RON octane mentioned in the owners manual with R+M/2 octane that is sold in the pump. 95-99 RON is roughly equivalent to 91-94 R+M/2) -------------------------------------------------------------------------------- After trying rocket fuel for two weeks, I can only say I love it. The first tank, however, was a disappointment. I think I did not add enough of rocket fuel for the first tank. So I added a little more for my second tank, it ran better but not too much improvement. Then on my 3rd tank, what a difference, the car feels like a "Rocket" now, even though it is an "Auto". I always feel there is more power available for me. I think for my 1st and 2nd tank, I did not have enough rocket fuel in it, even though I added one gallon per tank. Then, on my 3rd tank, I had enough because of the left overs from my 1st and 2nd tank. (I fill up my tank at about the 1/4 mark). Now I only have about 2 gallons of rocket fuel left, I better get more now!!! :-) -------------------------------------------------------------------------------- Reference materials: 1. Gasoline FAQ 2. McLaren Honda Turbo - a technical appraisal Ian Bamsey ISBN 0-85429-840-1, published 1990 3. Chevron's excellent Motor Gasolines Technical Review Jon Jacobs 86 745i (Das Rocket) 16 psi+ Boost with Team WWW.745i.com Performance Parts |
| scottie | Nice friggin post! It's only noon and I learned something new today. Now I can start drinking! Scottie Sharpe Sysop 84 745i 85 535i |
| Jens | I did not have the pations to read an 8hr post LOL Sincerely Jens |
| Bob745_Dallas | Outstanding! That's exactly what I was looking for. Thanks Jon. |
| dnliii | youdaman Jon |
| tritterbrew | Hey Jon, Great information! What about storage of Tolulene? What's the shelf life? Is it hydroscopic? I did think that Tolulene was a carcinogen but I'll need to re-check. Really interesting stuff! Thanks. Ted R. '84 745i |
| ra0507 | Bob, I can tell you where to get race fuel in Dallas. All the way up to 105 Octane unleaded. It is fun. Anybody have any idea what kind of power you are getting when running 20-21 psi? Jon86 745, I am not familiar with your boost controller and solenoid valve set up. How do I obtain info. Rick email: rkapurchasepool@aol.com |
| Jon 86 745 MS | You can not run controllable boost on the 745 with out some kind of wastegate modefication. The wastegate mod that we do at Team 745i.com allows you to run a boost controller either electronic or manual (We do make a manual unit). THis allows control of boost from inside of the cockpit. With our sustem we still use the Solenoid set up from the factory. This allows boost to begin to build around 1800 rpm (boost is anything over 0 gauge pressure). High octane fuel will allow you to run higher boost without the risk of detonation but only if fuel ratios are correct. Higher octane allows the system not to retard the timing as much allowing higher power settings. Hitting peak boost points of 20 or 21 psi for only a moment will not hurt as long as fuel ratios are correct. Maintaining boost pressures at this settings however will cause problems with the stock head gasket witch was not meant for those types of pressures. Jon Jacobs 86 745i (Die Rakete) 16 psi+ Boost with Team WWW.745i.com Performance Parts |
| clawson3 | I looked for Toulene at Lowes and Home Depot, the cans had some it in nut had other chemicals in ti as well. I assume you should look for 100% Toulene? |
| Jon 86 745 MS | Cliff, did you get the car running better? Not leaving you stranded? As for the Toulene I have never found 100% pure stuff. Most is around 98% or so. I have stopped using 105 octane blends as I have an O2 sensor for the Halmeter. I as of yet have not had any problems with 93 octane fuel with 1.2 bar of boost. No pinging etc. I do though know my injectors are flowing well and I am running 90 psi on the rail. |
| clawson3 | No unfortunately the 745 still won't start. I had the battery tested today and it was bad. Put another new one after I made sure it was fully charged and still won't fire off. I was wondering about the Tolune for my vette. I buy the 93 octane for it but I think some unscrouples gas stations give you 91 and call it 93. I get some ping on hard initial acceleration and so am sure the knock senosrs are retarding the timing. |
| Jon 86 745 MS | What year Vette? If it is one with a distributer try retarding the timing a few degrees. Can you get 93 Octane in Arkanas? Last time I was there it was only 91. I think it's time to try the OBC. |
| clawson3 | It is a 2002 coupe. I seems like CITGO is the only one that has genuine 93 octance. The others say they have it but it pings when I fill up there. I think they are just clipping the customers and giving them 91 with a 93 label. The dealer says it is mild, I think he is too lazy to replace the rear knock sensor. Anyway, thought ai would see what it ran like with a Toulene mix for kicks. |
| Lynn | [quote]Originally posted by Jon 86 745 MS
Team 745i.com now has the in cockpit boost controller available for shipping. Please contact us for more information and pictures. Jon Jacobs please may i have a quote on wastgate mod. ,fuel regulator ,boostcontroler in cad and chip/software. Thanks Michael West @ 603 763 3285 or l.west@erthlink.net |
| scottie | Hello Michael! Check out this post. http://bmwturbos.scottiesharpe.com/topic.asp?TOPIC_ID=3197 Also, just a hint for "newbies"; I do not usually recommend posting email addresses or phone numbers on the board because low life scum (i.e., spammers) troll the board looking for email addresses. I have special software to protect your personal information. (click on the icon to send an email to someone and the board will not reveal your true email address which is in your profile. -- or you can use in-board messaging, called "private messages". Also, just a hint, you can go back and edit your posts by clicking on the edit icon on any old post.) |
| Vern2765 | quote:ConocoPhillips sells unleaded 105 (aviation fuel). Here in Southern California, it is pretty close to $9.00 a gallon. I run a 25% blend with 91 octane, for about a 95 octane mix. I've run toulene in my previous 745i with great results. It is currently a bargain compared to the 105 octane gasoline. |