Unleaded Race Fuels

[Dieseltrain]

Hey guys,

Im at the point of trying some good fuel in my soarer. I just wanted some input and advice on what i could/should/Should NOT use

Please bare in mind i dont have programmable management, so something that will basically raise the current threshold of knock levels and a slightly more aggressive fuel!

At the moment, my tuner says from 5200 onwards, i need to pull some timing out of it, or run some decent race fuel to take advantage of it.

SO far people have recommended VP100 or Martini 102 and, a 50/50 mix of Martini M110 + Shell 100 fuel.

I know AFR's are important. I dont have a new graph with AFR's but i can tell you the figures... When Boost hits @ 17psi up to 5200rpm they are in the mid 11's. From 5200-7100rpm they are at 12.2-12.4's.

Any input would be great guys. If i had the $$$ i would try them at different race meetings and see a difference, but at $140-$165 for 20L that is not a cheap excercise for me to take! After all, i have built this on a budget

Cheers, Daniel.

[Joshstix]

The problem you're going to run into is that most race fuels have significantly higher density and much higher octane than pump fuel.

Why these two things are a problem for you is that with the same management you're going to run richer on race fuel, which isn't ideal as you're currently running mistures that will get you maximum horsepower. Plus the race fuel burns slower due to the higher octane level meaning that if you can't get some more ignition timing into it you're going to lose power due to the combustion process occuring later in the crank rotation.

Basically what I'm getting at is you want to run the lowest octane that is safe for your setup. If your current setup runs perfectly on 100 octane fuel with no pinging then bumping it up to 110 without making changes to the management will reduce power.

Personally I'd keep an eye out for a cheap aftermarket computer as I suspect you'll be able to get more gain from that than race fuel on the stock management.

[Dieseltrain]

I still have my FCD ( not kooked up ) i can throw on there and see how it goes. We tried it on One Run, it was making almost 10rwkw through the whole rev range up till 5200 when it started to knock, so we backed off and disconnected it.

It wasnt fuel related, the afrs were still good, but the timing was probably a little aggresive. Which is why im asking about fuels.

I should have mentioned that,hehe.

[The Real Roadrunner]

id probably give the martini 102 a go as its not bad for reducing knock and isnt too badly priced but josh is right that you will see more of a gain on an aftermarket ecu.
my tuner at unigroup has martini in stock and said thatt hes seen some good gains out of it in SR20s (and they love to ping there arses off)

at the end of the day id trust the tuner if your getting good results out of the rest of the work hes done and see what happens.

keep in mind if your paying $140 odd for 20L it will quickly add up to the cost of an aftermarket ecu.

cheers
linden

[oldeskewltoy]

I know AFR's are important. I dont have a new graph with AFR's but i can tell you the figures... When Boost hits @ 17psi up to 5200rpm they are in the mid 11's. From 5200-7100rpm they are at 12.2-12.4's.

Hmmm sounds like you might be beginning to run lean??? Maybe a 10% boost in injector volume... or maybe a fuel pressure riser???

[Norbie]

It sounds to me like you're already in the danger zone with your stock ECU. My advice is not to push any further until you have proper management.

[Dieseltrain]

Danger zone? My tuner says anything 12.0-12.5 is good!

The FCD didnt actually change the Afr's much if any, but it does increase timing.

And i see Yavuz at Unigroup also He mentioned the M102 for a try!

Im understanding where your coming from with the management side of things, in the pipeline might be something like a Greddy EMB.

Im trying to see if fuels really have anything to do with the same tune! I guess there is only 1 way to find out.

[YLD-16L]

Im trying to see if fuels really have anything to do with the same tune!

This link below is an example of what is achievable when stepping up from PULP 98 to 100+ Octane fuel. It also does a comparison between 98 and 100 with no alteration to the tune. Obviously the programmable management allowed them to take full advantage in the other parts of the testing.

V-Power Racing fuel comaprison

For shits and giggles last weekend I ran a tank of V-Power Racing, added 5 degrees advance to the ignition timing (keeping a close ear on knock levels) kept boost (16.5 psi) and AFR (11.8 @ WOT) both the same as previous dyno runs and made no extra power. Given it was a dyno day I got no chance to play around with anything on the dyno but I'd love to do a tune on a 100+ octane fuel, obviously you can't tune an ignition map properly on the open road so I was just adding a little to see what would happen

I just did the above because I knew what power I'd make with the usual tune and thought I'd have a play - I had nothing to lose really.

Nice work on your times on the strip too, very impressive.

[The Real Roadrunner]

For shits and giggles last weekend I ran a tank of V-Power Racing, added 5 degrees advance to the ignition timing (keeping a close ear on knock levels) kept boost (16.5 psi) and AFR (11.8 @ WOT) both the same as previous dyno runs and made no extra power.

just be careful with the vpower from shell, cause if it sits in your tank for about a month it will actually then have the octane rating of a std ulp. there have been a few engines ive heard of lunching ringlands cause the cars are only driven 100km or so a forghnight and after 2 weeks the owners have commented that they can hear a faint rattle from the engine up top.

cheers
linden

[Dieseltrain]

I do over 500km's a week in my soarer, the fuel has no chance of going bad. but thanks for the advice.

[YLD-16L]

just be careful with the vpower from shell, cause if it sits in your tank for about a month it will actually then have the octane rating of a std ulp. there have been a few engines ive heard of lunching ringlands cause the cars are only driven 100km or so a forghnight and after 2 weeks the owners have commented that they can hear a faint rattle from the engine up top.

Thanks for the heads up Linden, my car often sits for weeks at a time so this is a problem that's good to be aware of.

[Dieseltrain]

Ok, Anyone used or heard much about the VP SV-05 Fuel? Supposedly it has little oxygen content and has an extremely fast burn rate. Used in quite alot of high comp race engines.

[chris davey]

How can you guys say that an ecu would be more beneficial if daniel is saying that the engine is knocking at it's current level. Means if he uses current fuel and a programmable ecu that he would have to retard timing (usually reducing power).

I think that if you run a race fuel that has similar oxygenation to your current fuel (therefore keeping same afr's) but with the increased octane "should" mean that the knock dissappears at the same ignition timing. You never know, with the good fuel the knock sensors may not register at all and it may run even more timing than now?

re fuel sitting: I think that happens with a lot of fuels. My car sits around a lot so I just always make sure that it is all mainly used up without any hard engine work and it is fine.

[1JZ-Rolla]

How can you guys say that an ecu would be more beneficial if daniel is saying that the engine is knocking at it's current level. Means if he uses current fuel and a programmable ecu that he would have to retard timing (usually reducing power).

Chris I guess it depends on Dieseltrain's actual aim here... make more outright power or stop knock only?

The lean mixtures above 5200rpm may be contributing to higher combustion temps, reducing the knock threshold for a given timing value, so it may not be the timing alone that is the problem. So you can either maintain the same AFR's and try to fix the knock with a slower burning (higher octane) race fuel, or keep the same fuel, and retune (via aftermarket management) the fuel delivery to bring the AFR's back down, potentially alleviating the knock without reducing timing much (if at all).

I guess its hard to predict which approach is going to yield a better power result, but I know i'd be more comfortable controlling my engine throughout the rev/load range with programmable management rather than using race fuel as a bandaid for a problem only occuring around peak power.

To ramble further and throw in another aspect, "if" Dieseltrain's main objective is to run quicker times at the strip, will this be achieved only by running race fuel for more peak power (without knock), even if it means sacrificing midrange where there is currently no problem with the AFR's or timing values? It's power under the curve that wins races, not peak power.

[jonchai]

Interesting thread
*subscribe*