Got Race Fuel?

[two40]

Do some of you use race fuel on the Street? When I say race fuel I mean something within reason and within law.

 

Basically I'm asking because the car that I've just bought is tuned at 10.8:1 compression, Cylinder comp test done and all 8 came up 195-200 psi. The previous owner used pump fuel at 98RON (max available) and an octane booster which probably doesn't help much. In fact, I've heard that it does damage when using it all the time. Is this true? So anyway, I wanted to use a street legal unleaded race fuel and where I'm from (Australia) we have some of the more popular race fuels but obviously not all. From the quick research I've done I can get my hands on Elf, Sunoco and VP.

 

Which fuel is the better to use and at what RON rating should I aim for? I guess that'll ultimately come down to my mechanic but I'd love to hear your opinions from the limited information I've provided.

 

Cheers

George

[two40]

btw, sorry to the mods if this is the wrong section for this thread. Please move it if necessary.

 

Cheers

[Scottie-GNZ]

George,

 

not sure how much help you are going to get here as you have several brands we do not have and are not familiar with. What I can say is do not waste your time on money and octane boosters. Also, since you are after the most octane you can get on the street, focus on the Motor Octane (MON) rating of gasolines as that is the only meaningful one for high-performance. This might not help you much, but here is a little chart I maintain that compares high-octance fuels.

 

http://www.turbobuicks.com/members/scottiegnz/Racing-Gasoline-Chart.htm

[Guest Anonymous]

First off let me suggest your local small airport. The last I knew the octane there was like 102-104 but with such pressure that is probably not good enough!

 

Now, I would say that since you measured such a high compression (and it is really HIGH), drop back in your thinking to cam duration. It sounds to me like someone has maby gone crazy for a lot of compression without the cam to match it. Perhaps you have a stock cam still in there and if so the compression is probably way over what the previous owner intended because unknown to him there is little compression loss due to cam duration (which is a part of the whole). That pressure should never be over 200 and 160-70 would be most for street. Maby this guy was racing with alky or something. Don't drive it like that, it wont last.

 

The thing dosen't make much sense I must admit. Such pressure is completely impractical for the street and even if you cammed it down with more duration it would lope at Idle like a horse with a broken leg.

 

The idea is this: When you raise the commonly aknowledged compressio say like from 8.5:1 to 10.5:1 (the max I would ever recommend for the street) and kept the same cam, I would say you raised it 2 points and wer borderline on the best pump gas. If however you cammed it properly the pressure would come back down about 2 pionts again to around 8.5:1. Then if you got an itch to get the C/R actually up to 10:5 with the better cam left installed, you would have to go 12.5:1 but, this is not for the street. So we put in another cam that takes you down again 2 points to the desired 10.5:1. Now that's it and you would be saftely "Borderline" on aircraft fuel probably (Preimum pump gas in a pinch). A lot depends on how long you want the engine to last and/or how much ignition retard vs power loss you are willing to accept to prevent detonation.

 

All this camming is done with increased intake valve duration as a basic thought and the more duration you add the lopier the idle will get and the mushier low end power will get.

 

Lastly. if you have an auto trans then you will need a new matching "Stall Converter" to match the cams power curve if you want any performance off the line. Standard? Just slip the clutch.....LOL

 

There is another fix and that is water injection. That might interest you. Such would probably allow a 2 point increase above normal fuel ratings.

[two40]

...since you are after the most octane you can get on the street' date=' focus on the Motor Octane (MON) rating of gasolines as that is the only meaningful one for high-performance. This might not help you much, but here is a little chart I maintain that compares high-octance fuels.

 

[/quote']

 

That chart is great. I've a few friends who would be interested in it. Cheers. Looking at the chart I can see some fuels have a higher MON than others while retaining the same RON. Are these the best ones to use?

 

Do you know when/if you will be able to update the last two fuels? It's the Sunoco GT unleaded and unleaded +.

 

 

SPIIRIT, the airport which is 2km from my house sells fuel with lead in it. I don't really want to run it with that but it seems like the cheapest option.

 

I took the car around to a performance workshop and the owner heard the engine for two seconds and said 'It's overcamed but there could be more to it than that'. He needs to pull it down which I'll let him do in a while. The tappets were noisy but he also put that down to the nature of the setup, maybe.

 

Thanks for your lengthy response, I'm still mulling over the info. The figures don't make sense to me either.

[Guest Anonymous]

Ya two40.

 

Well, if he said "overcamd" that quick then maby you have a tiger by the tail. In other words the cam work was done along with the head/piston/ compression ratio setup. I would hunt the seller down and get the real skinny on exactly what you have in there, it sounds like a very strong engine potential. Al

 

Maby a good "Race Tune" (along with the proper fuel is all you need, but like I said, that high pressure is going to get you without the best special fuel as far as I know.

 

Without much info I went for broke as Iguess I assumed you were a do it yourselfer. If you have the green to get a tune at that shop then go for it!

 

Skip the details about the ratios I wrote, the tuner probably knows all about it anyway.

 

The tappet sounds mean you have either mechanical roller tappets (Very good for best power and low friction losses) or solid lifters (more friction loss but most effective for power). It's either like that or the valve adjustment is way out of whack. There are so many possibilities I will not get into here (Hence the recommended tuneup).

But, If the tappets are like I say then the noiser they are the more power you are losing (but then again they may be adjusted loose to compensate for sometning els that is not quite right, who knows at this point)?

 

Offhand, I would say things are looking good for you in the engine department (Barring any suprises).

 

One last thing. If this engine is a well put together race engine, be careful who you let work on it! A lot of mechanics are all thumbs when it comes to such engines and will screw them up fiddling around and blame the engine for that. I am sying this because of what you mentioned about the place you went to commenting on an "overcammed" condition. This does not sound like a professionally experienced race engine mechanic to me because all race engines sound "overcammed" even when in tune (except to those with a practiced ears). In other words he apparrently didn't know what he was listning to except for the tappet noise.

 

I hope this dosen't happen to you! Find a recommended race tuner is all I can say.

 

Does this engine have an above normal idle and go rump rump rump or blap blap blap?.....LOL

[two40]

I wish it was a tiger I was holding by the tail. It's making around 290rwhp and all signs point to even more power which is not there. I think it's out of tune is all. I spoke to the person that originally built this car and engine and he doesn't recall everything but he did tell me that all internals have been improved/reinforced. Says the cam is an Isky 262H but can't be sure. He did have a spec sheet written up which he gave to the previous owner. I'm trying to get a copy of it now. Should clear things up a bit.

btw, this car was built with track in mind and has always been tuned as such.

 

Re the tuner. When he made that comment I think he was implying for street purposes. I didn't tell him my intentions or any history so he was just making an observation without knowing it's meant to be race tuned. This guy builds 9 second engines on a regular basis, comes very highly recommended so I'll trust him with it. Just hope my wallet is fat enough at the end of the day.

 

Let me find out some more info onthe engine and I'd love to see what you have to say.

 

And that blap blap noise you mentioned , it makes that but not as severe as some other 350's I've heard. It is pretty lumpy though.

 

Cheers

George

 

oh, one last thing. The mechanic did also say that the engine doesn't pick up and drop off revs quickly enough for the cylinder compression it has. *shrugs*

[Guest Anonymous]

I am standing by.....

 

OK two40;

 

I am glad to hear you have a real experienced "Tuner/engine builder" at hand. I am releived! Treat this man like royalty with your best foot foreward (Showing much respect) and he will reciprocate with most info you may ask for as time goes on.

 

His comment about the lack of "snap" to the engine is probably about not only a lack of tune but also likely a purpousfully retarded distributor done by the person you purchased from and/or his friends to compensate for that high compression so he could run pump gas (God only knows).

 

Once an engined is truly modified, it is no longer "Just an engine" but has become a sophisticated item only to be played by the skilled. The tune has become most critical in point and even a small discord will have a drastic effect on both top and overall performance. The opportunity you had to purchase this car probably came out of the frustration and confusion others have had trying to get itn running right.....LOL.

 

Interesting that you mention it has an Iskenderian cam, you couldn't have better. One bad thing about cams is that they can be "Over-revved" by a heavy foot which causes valve float and in turn a hammering down of the critical lobe surfaces. This means the cam lobe can't lift the valves as high. Power and accelleration bigtime loss is the result and would become obvious if you were the owner at that time. Over-revving is easy to fall into and I am quite sure your engine has had it's share in inexperienced hands already. This is why we always use the "redline" as an absolute danger limit and never exceed it! You've got to know where that line is for sure. Too late for you now I bet. I expect you will get this report from your Tuner (among other things), let's hope not.

 

If the tuner says the cam is shot, beleive it. If he says you need a new cam, springs etc. beleive it. The cam is like the heart of engine and must be in top shape for top engine performance. This means $$$ out of pocket initially but with proper care, a fruitful and satisfactory result long lived. Ever loaned a tool or something and have it returned damaged and/or useless? Assume this with your engine and you probably won't be far off.

 

I will tell you a story about used cars. Many used car dealers seek out a slick mechanic, unscrupulous and full of tricks. The idea is to fool the public into buying a car with a bad engine. One of these tricks is as follows: The engine has a mild conrod knock (critical damage and/or wear and won't last much longer, particularly on the freeway). This knock would even be questioned by a woman. So what the mech. does is loosen up all the rocker arm adjustments so the thing makes a nice loud ratteling noise which hides the knock. Then a very tempting price is place on the car and if questioned about the rattling the dealer says "it only needs a valve adjustment, do it yourself or take it to a garage, it will only cost a few dollars.....if it bothers you that much, it's really a very nice car". Hmmmmm. I could say on but I spare you.

 

Looking in my motor manual I see that a 1970 350 V8 chevy with a 4 barrel carb. and 11.0:1 compression is making 370 advertized horsepower at 6000 RPM. Your engine even if stock might have (with 15% friction losses deducted) 370 - 15% = 315.5RWHP. Add only the extra equipment you are aware of and I would put you at around at least 336RWHP in top tune. I am not pushing. This is a very conservative estimate! And if it is bored oversize and/or stroked a little? What then? This is why you need to get the dope on that engine! If you don't know what you got you can't know what to expect and the numbers don't mean anything because you don't have a BASE to work from. Know what you got and then you have the base and can be realistic about what is going on. By the way, does this engine have headers and dual exaust by any chance? And surely get that dope sheet!

[two40]

G'day Spiirit

 

This tuner is a really nice guy. Just the other day I went around to his workshop and after he'd finished there was around 7 people sitting around and some were telling stories. Some of the stuff that he's done in his life is enough to excite and inspire anybody.

 

I'm going interstate today to sell my original Z (wish I could have kept it as it was in great shape) so I'd better make this quick.

 

I have not overreved it yet as I've not had the opportunity and had I had the opportunity I still would have been kind to it. It's still unregistered so I'm only, by law, allowed to drive it to the mechanics and back. I'd hate to have it impounded before I have some fun with it.

 

I certainly hope the cam is not shot. It's only 9500km old. The car has not seen much of the road since being built. Thes two previous owners sold it out of lack of time to enjoy it more than anything. The previous owner used it for track work and was frustrated at the not so high power levels.

 

As I said before, all signs point to more power which is not their so I think you might be right about it being out of tune. A friend of mine who came up to look at it and had a go in the passenger seat was also dissapointed at the power it put down.

 

Yes it has headers and dual exhaust. Oh, and it's got 50 thou overbore so it's a 355. I'll stop throwing numbers and specs around now until I have the complete story.

 

The previous owner has the spec sheet so now I'm just waiting for his e-mail.

 

Cheers

[two40]

Hi Tom.

 

Finally after giving up a friend of mine across the country found an article in a mag that's given me some insight.

 

Here are some of the details:

 

11:1 forged pistons

steel crank and X series conrods

balanced bottom end

big block oil pump

isky hydraulic cam (262?)

Speed pro lifters

TRW pushrods

750cfm holley

MSD electronic ignition

Weiland X-ellerator polished alloy intake manifold

 

So what can your freakish mind come up with from this info Tom?

 

Cheers mate.

 

ps, the exhaust guys fixed a heap of cracks in the extractors and a flange gasket leak too. Runs alot smoother now.

[dot]

Hi George:

You might want to search this sight for a thread on water injection. I found that a Edeldrock water injection kit was a good cure for a big block I had put together with a bit too much squeeze. I doubt the kit is still around but there might be something out there.

Cheers: Glenn

[Guest livewire23]

is this a SBC 350 we're talking about? Because everyone speaks like 10.5:1 is a lot of compression, but for a H22 the stock motor runs 10:1 and the JDM version runs 10.5:1. My car is 9.8:1. I know preludes and civics around that are running around 12:1 on pump gas. But I suppose its probably different in a 350.

[Guest Anonymous]

Livewire23;

 

Yes it is a 350 SBC.

 

The compression numbers you are throwing out are Static numbers and are the popular Democratic way of discussing the subject. However, these numbers do not reflect the Dynamic compression which occurrs when the engine is running.

 

Let us say with my engine for example, I say I run 10.88:1 on pump gas and let it go at that. But this is just general street talk and far from the whole story!

 

Actually the whole story is that I am running 10.88:1 static and 8.5:1 dynamic and not on just "pump gas" but Preium Pump Gas. I would ruin my engine on regular gas!

 

Yes, we are splitting all the hairs here, but in the process, something very interesting has come to the surface! The difference in the two ratio's I mentioned is a reduction of 2.38 points. This reduction in ratio has been caused by purposely tampering with the intake lobes of the camshaft so as to move the power range of the engine to a higher RPM. In this case, since we know that this tampering will reduce the Dynamic compression ratio by 2.38 points (to 6.12:1), we alter (reduce) the combustion area by the necessary amount, to restore us to 8.5:1 Dynamic. During this process the Static has also dropped from 10.88 to 8.5 and back to 10.88 again. And so we have our cake and eat it too.

 

I'm not going any further but this is the crux of the matter you inquire about in here.

[Guest livewire23]

hmm, now there is something I wasn't aware of before. I just assumed the compression ratio stayed the same no matter what. Of course when I said pump gas, I meant premium fuel. Those cars would knock themselves to death on regular gas.

[Guest Anonymous]

Livewire 23;

 

Ya, the subject is very interesting. For example: The rules for Preimum pump gas are (and have been for many years), 8.25:1 optimum and 8.50 maximum. No production run vehicles are designed or built to use higher than that. Any car that is running a 12.00:1 Static ratio on preimum must absolutely have some method of cooling the intake charge to make this possible! Now I don't know everything by a long shot and am not up on the latest DOHC and Turbo engines but I will say this about them: No matter how exotic these engines get it does not give them license to break the compression laws of 92 octane gasoline!

 

Now as to your own compression.....There is room for a nice performance boost there. If you do a Compression Pressure test on your engine I'm sure you will get readings around 150-160 psi. This can be saftely raised to 170-175 (on premium only) and you will notice the difference. Interested?.....LOL

[two40]

Hi Tom. I got your email and once again, thanks for educating this poor fool.

 

I'll be shopping for the comp test gauge next weekend so we'll see what comes up then if I manage to find one.

 

Btw, our max pump gas is 98RON. Is it the same out your way? Just making sure we are comparing apples to apples.

 

 

George

[Guest Anonymous]

George:

 

I don't know zilch about any RON George, clue me in? We have a 92-93 octane ratimg here is all I know

 

I been thinking. I read your original post that said you had 10.8:1 compression ratio and ..... there it was again.....the thing that set me off in the first place, 195-200 compression pressure! Now you have verified 11.00:1. Anyway, with 195-200 psi you definitly have a fuel problem reguardless of my previous conclusions! What I really don't understand is how you can have 11.00:1 compression pistons, bring it down with a 262 intake lobe duration at least 2 points and still have such a high reading of 195-200 psi. Your Dynamic compression should not be over 9.00:1 for sure. Now I am thinking the cam has been swapped out!. Get a dial indicator on that cam and see what the intake duration is. I bet it's not 262 anymore! If a stock cam has been stuck in there then you may have 13.00:1 instead of the numbers you have been given. Something sure is amiss here!

[Guest Anonymous]

George;

 

Ah well.....apparrently you have not seen the 195-200 pressure numbers for yourself then. We'll wait and see what you really have there and hold on the dial indicator in that case! And George, maby I am the one who is a fool!.....LOL

[two40]

George:

 

I don't know zilch about any RON George' date=' clue me in? We have a 92-93 octane ratimg here is all I know.[/quote']

 

There are two octane rating systems used around the world. If you haven't heard of the RON (Research Octane Number) then my guess is you guys use the MON (Motor Octane Number). Some countries even use the average of the two which might be the case out your way.???

 

Can someone tell us what octane rating system you use in the US?

 

RON = indicates fuels ability to resist detonation during acceleration

 

MON = indicates fuels tendancy to knock at high engine speeds

 

Cheers

[Scottie-GNZ]

We use the average of the 2, advertised as R+M2.