Highest "safe" compression 2E motor

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alfaquad
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Re: Highest "safe" compression 2E motor

Postby alfaquad » Mon Jun 05, 2017 2:24 pm

AlexTDi wrote:
alfaquad wrote:Why do you keep wanting to run 95 or 95 and mix? There are other options available that are much safer and will make more power.

Measured the head cc on my head the other night - 27cc - which basically worked out to 13.45:1 CR on my car. Remember I don't run 8v pistons. I'm giving up on that head though, too much wrong with it and too expensive to try fix it. Sarel is busy doing a proper Stage 3 head for me now, with rev kit, semi solid lifters and 298 hydraulic cam. If I am still struggling to make power, it just means my bottom-end is stuffed. But I can live with that till I can afford a proper bottom-end.

Oh and what happened with your box? Find any drag on there? My box is in pieces at the moment, and I finally figured out why I get so much wheelspin - there is no LS-Diff in the car.

Lots of work before I can get my car on the track by the 16th!


I can't get avgas as easily as you do so for now 95 + mix will do, my car is supposed to make decent power on just 95 so ya, the head he is building you is exactly what he built for me. it's still at the shop as I got them to recheck it and skim it further. will collect it this week and try it again at a later stage.

Box is fine drag is just as low on the dyno as a normal link shift, so that's not the issue. I'm semi-sorted with the suspension setup now ran a 1m18 flat two weeks back at Zwartkops on old tyres so relatively happy that I'm progressing.

LS is for girls! :lol: you don't need it to be quick in a Golf and you're closer to Superhatch spec :wink:


I saw you ran at the Michelin Cup event yeah.

Yeah, head is basically the same, except that mine will be over 13:1 CR and ported for the throttles (different to single throttle body).

It's easy to get fuel, but it just requires someone to go fetch it. We take turns to go get, but we buy a lot at a time (500+ liters) so only go every few months. I don't like mixes.

LS just makes a lot of things better - if I was running Superhatch spec or Challenge spec, sure, but with the way my car is set up it gets wheelspin everywhere. I could tweak suspension setup to eliminate wheelsping mostly, but I would rather have one - suits my driving style more - car is already damn loose and without the LS I can't get on the power as early as I want, nose just pushes wide on the exit. LS will remedy that. I'm quite confident that I'd be able to do 13s with my car with not much more power than I have at the moment, just need to be able to put the power down. My apex speeds are already basically on par with Keagan's CRX which runs 225s, but because I have to wait to get on the power, my straight line speeds suffer.
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Re: Highest "safe" compression 2E motor

Postby PaKiMoNSTeR » Wed Sep 06, 2017 12:44 pm

Old thread revival...

We changed a few things on the car since this discussion and the last post in my thread. But I have been wondering about fuelling volume. So with the stock injectors we started running a 15l:5l 95ULP to Toluene mix. The main reason was not for more power rather safety. Then the TPS stopped working and there was a VR6 throttle lying in the garage so it was decided to fit this along with a different intake manifold and larger injectors. 444cc to be exact. This was also run on a 15l:5l ratio mix. No power gain was made, in fact we got less power out of it. However a little more torque was achieved.

So onto my actual question. How will larger injectors assist in reducing detonation or will this not have an effect? The timing on the car is vey low and they can't advance it even with the larger injectors as there is some ping. Will larger injectors assist or is this not the answer. The fuelling is way rich at the moment and we have gone back to smaller 250cc injectors and the car is getting mapped again. I just want to confirm that throwing more fuel at it will or won't make a difference. Is the only answer more octane or a more aggressive mix/type of fuel the solution.
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Re: Highest "safe" compression 2E motor

Postby panic-mechanic » Wed Sep 06, 2017 1:23 pm

Oh holy carp. Everytime anybody asks this question like this I want to head for the hills. From a casual observer point of view it would look like you know quite a bit until you start asking these pointed questions and then I get very scared. So from what I surmise is you had a car tuned on a certain throttle body and injectors. You then put a different Tb and much larger injectors on but did not remap it, expecting much more power.?

The explanation of why engines need only a certain amount of fuel and why simply throwing much more fuel at it comes down to the very basics of an engine and WAY WAy WAY more space and time than what I have here for.

But in short. A given engine using a given fuel will only make maximum power at one given air/fuel ratio. adding more fuel will lose you power and taking away fuel will lose you power. Hence to make more power you first need to get more air into the motor and that is the hard bit.
So yes you WILL lose power by just putting big injectors on. And even if you have 2000000000cc injectors the engine can only use x amount of it and that is at the correct air/fuel ratio. That ratio is determined by the fuel composition and set for your motor by the management system /carb by tuning it on a dyno until you observe the most amount of power produced.
Detonation on the other hand is an affect or combination of the Fuel you are using's ability to suppress detonation(octane number) the effective compression ratio and the amount of ignition advance used. Indirectly air/fuel ratio has some affect on it but is not that important and on it's own will not solve detonation. It is easier to suppress detonation by either upping octane, dropping cr or retarding ignition timing. But you can also only retard timing to s degree before it has an effect of reducing power and allowing EGT's to climb.
These are all concepts one would expect a guy that fiddles with racing engines to know and especially a tuner to know. If your tuner cannot explain this then I suggest you go find another.
I actually have a training document that was written around the management tuning that I used to give that explains all this in very very clear minute detail but I dedicated months of my life on it and some people think it should be given away for free and I don't agree so sadly it lives on my hard drive without ever seeing the light of day on a forum like this.
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Re: Highest "safe" compression 2E motor

Postby panic-mechanic » Wed Sep 06, 2017 1:46 pm

I am glad you ask though as it means you are thinking about it. It is that that they are very complicated subjects that is not simple to quickly explain.
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Re: Highest "safe" compression 2E motor

Postby PaKiMoNSTeR » Wed Sep 06, 2017 2:21 pm

My skill set lies somewhere else, not sure where, but not with cars. I'm not totally clueless but I'm learning as we go along. Perhaps my message was not 100% clear in the way I tried to put it across. Yes we fitted a bigger throttle as we had one lying around. Bigger throttle would mean a larger volume of air so bigger injectors could potentially assist in making more power. But this was not the aim. It was fitted only because we had TPS issues and we had these lying around so instead of buying a new TPS we fitted what we had. After fitting these bits the car was mapped again.

My real question was would a larger volume of fuel assist in reducing ping. As this is the main reason why we are not able to make more power. CR is at 11.4 or less so there should be room for more timing. From your answer above it would seem not. So, we have to go and search for some other reason/solution as to why the car pings.

It's going to another tuner to get mapped this week with smaller injectors so let's see where end up...
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Re: Highest "safe" compression 2E motor

Postby panic-mechanic » Wed Sep 06, 2017 3:19 pm

Injectors large or small is not the solution. Higher octane fuel is the answer or reduced compression.
What total timing are you running at rpm
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Re: Highest "safe" compression 2E motor

Postby AlexTDi » Wed Sep 06, 2017 3:44 pm

On my motor 11.4 compression I ran 95 + NF Ultra race with stock injectors and they weren't maxed out on their duty cycle or even close. If I recall correctly timing was fairly high at the higher rpm 5500 - 7000 between 28 - 32 any higher and it would ping.
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Re: Highest "safe" compression 2E motor

Postby panic-mechanic » Wed Sep 06, 2017 4:10 pm

you are in jhb- he is at sea level. 28 -32 degrees are a lot anyway - even if you can get more you are already at the point where power will start to fall off if you advance it more if it was not pinging.
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Re: Highest "safe" compression 2E motor

Postby dubz-on-drugz » Wed Sep 06, 2017 6:49 pm

So pinging is pre-detonation , adding more fuel probably does not help you any more then changing fuel brands, I have the exact same issue on my 1800 8v with 288 cam . I also feel that I could get more if I was not limited to pinging.



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Re: Highest "safe" compression 2E motor

Postby panic-mechanic » Wed Sep 06, 2017 8:00 pm

So again. Either up the octane or drop the CR. those are the only two solutions if you are 100% sure that you think it will keep making more power with more timing. PLEASE PLEASE PLEASE remember there is a logical point where more timing advance stop working. So don't think you can keep adding it indefinitely and it will just keep making more. Depending on the actual fuel and burn speed of it that it will make less power with more advance.
So the thing timing advance achieves is a fully burning flame front by the time the motor reaches TDC. So there is a mechanical limit anyway.
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