leaded vs unleaded gas

[av8rds]

would I expect any problems running 110 leaded race gas in a 393 efi stroker?

I have a small case of detonation under the light load/partial throttle. My engine builder( took out some time a few years ago but it didnt solve the problem. I just put in a colder set of plugs and that too did not solve the problem. So I wanna try a little race gas mix as I found octane boosters dont work. I can get some 110 leaded right now and want to make sure there wont be any problems.


thoughts?

 

[Socal Tom]

I would try blending it with premium pump fuel. Octane can be calculated by taking the weighted average. 5 gallons of 91 octane, plus 5 gallons of 110 octane gives 100.5 octane. Have you had it dyno tuned?
Tom

 

[av8rds]

I would try blending it with premium pump fuel. Octane can be calculated by taking the weighted average. 5 gallons of 91 octane, plus 5 gallons of 110 octane gives 100.5 octane. Have you had it dyno tuned?
Tom

yeah I was gonna try as little as possible at first like 19 gal of 93 with 1 gal of 110 and see what the lowest combination of mix works, if it works.

I did have an engine dyno tune when built but its never been on a chassis dyno.

 

[Broncobowsher]

You said EFI on the stroker.
Lead contaminates the O2 sensors, killing them. So that would be a problem.

 

[Socal Tom]

I did have an engine dyno tune when built but its never been on a chassis dyno.

I'd consider taking it down to a chasis dyno and having them burn you a custom chip. They should be able to adjust the timing advance to clear up the problem.
Tom

 

[av8rds]

I'd consider taking it down to a chasis dyno and having them burn you a custom chip. They should be able to adjust the timing advance to clear up the problem.
Tom

thats probably the best idea...this is more really a short term experiment to see if I can get rid of it as I had thought the timing adjustment would have done it a few years ago. And really I'm kinda sick of having to baby it in certain conditions.

 

[gearida]

A knowledgeable racer told me that if you mix a lower grade fuel with an upper octane, you get the lower grade. it isn't like it will blend and become a mid range.

 

[Broncobowsher]

A knowledgeable racer told me that if you mix a lower grade fuel with an upper octane, you get the lower grade. it isn't like it will blend and become a mid range.

Your knowledgable racer does not know fuel. While not perfectly linear, blending fuels is really close. Gas stations only carry standard and premium fuels. Mid grade is simply a mix of the two. We just had a big stink at work and our local fuel lab was running overtime as there were fuels coming out of pumps that were not meeting grades across town. One was something like 12 points down on octane. The premium fuel was better then the race fuel. I know the next time I get some 110 for the bike, I will get a little extra for our lab and see what they really say it is. It is sure nice to have an onsite fuel lab at work. I would run it myself (I have run the older equipment before) but I am not autherized to run the new machines. But I know the guy who does run them.

 

[wildbill]

%) %) %) On the mustang 11:5 to 1 ued a edelbrock water injector and 91 gas worked good, Just get water every time you get gas. It was vacuum and elec came on at 1500 RPM up good luck. Bill %) ;D

 

[rjlougee]

Sean, can you give us some more specifics about the engine and the EFI setup as you have it installed? (10.5:1 with iron heads, A9x EEC, no Tweecer, etc...)

Unless you're running a really high compression ratio, I'd expect your spark map is really off, probably a bad "load" calculation. Timing is set to 10 degrees base?
Joe

 

[av bronco]

Instead of race gas you can tun toluene, it can be had at any paint store and frendly on o2 sensors. one gallon to ten gallons gas should clean up your pinging.

 

[av8rds]

Sean, can you give us some more specifics about the engine and the EFI setup as you have it installed? (10.5:1 with iron heads, A9x EEC, no Tweecer, etc...)

Unless you're running a really high compression ratio, I'd expect your spark map is really off, probably a bad "load" calculation. Timing is set to 10 degrees base?
Joe

Hey Joe, what do you know?

this has actually always been a problem, for the 8+? years I've had the motor

Actually I'm using FAST programmable EFI. 2 years ago when I took it to the builder and pointed out the problem he trimmed the timing through the range(2000-2400 part throttle low-high load), it didnt seem to make much difference. I didnt want him to kill too much of the timing and lose power so we left it at that.

I guess I should point out the caveat , my builder said 'its not detonation' He also couldnt tell me what it was if it wasnt.....sure sounds like it to me, but I'm not the expert, but it also sounds like det to one of my mechanic friends too. I tried a colder plug to see if that helped and it appears to make no difference.

So thats why I want to try higher octane, to kind of prove/disprove its det. My plan is if it goes away, I think I'll take it to a chassis dyno and another tuner and see if they can fix it on pump gas.

I'm trying to find my build paperwork, it got misplaced when I moved 5.5 years ago..

 

[rjlougee]

Sean, I'd really want to put a wide band O2 sensor on it and see what the air/fuel ratio is as it's making the noise. That's going to give you the best answer.

Which FAST setup are you running?
Joe

 

[av8rds]

Sean, I'd really want to put a wide band O2 sensor on it and see what the air/fuel ratio is as it's making the noise. That's going to give you the best answer.

Which FAST setup are you running?
Joe

Its the original not the new one.

 

[rjlougee]

Its the original not the new one.

Wanna list some specifics? I know the stock stuff pretty well, but not up on the FAST stuff, especially what's no longer on their site.

Is it a sequential system? Batch-fire or individual? MAF meter is under the air cleaner? Injector size, etc...? Does it do spark compensation as well or do you have a mechanical dizzy? What coil are you running? Anything else? And what're the heads and compression ratio?
Joe

 

[av8rds]

Joe I havent had a chance to find my spec sheet but it is batch, no MAF. I think the injectors are 30's, no mech dis, Crane ignition. For all practical purposes in this discussion its the same as the XFI. The XFI is just and upgraded version, not really a whole new product.

wellllllll things didnt go quite like I expected.....I mixed about 2.5 gal of 104 and about 15 gal of 92/93(whatever was in the tank).

It seems to me that it didnt get rid of the det but moved where it happens???????

I'm 100% sure it was between 2100ish and 2300 ish all the time, coulda set a watch by hit...now I dont have it there but I have it from say 2700-2900. I am 100% sure I had no AUDIBLE det that high ever.

I'm gonna go back and mix the rest of the 104 with whats in the tank and see what that does.

how that for a mess?