Using race fuel on boost !!

[mgbv8]

Its time to think about the next stage of my plan to run down to my old PB on the 1/4 mile of 10.2 seconds without any nitrous.

I made that PB with 10psi of boost and a 150 shot of gas on the old stock Rover 4.6 (with forged pistons). The new engine is much more efficient and has already run 11.2 with 6psi of boost only with 361hp. I reset the timing and fixed a dissy issue so it was running the amount of retard it should have and it then made 402hp on the dyno. I'm hoping that the extra 40hp might have been enough to nab another 10/th on the 1/4 mile pass.

I'm about 1 second off my old (nitrous + boost) PB at this time.

I'll be out later this year with 13psi of boost which I hope will improve things a bit. Maybe 13psi with 13 degree's of retard will get me to a flat 11 second pass??

This engine certainly seems to like running a lot more advance than the old stocker on boost.

I'm now thinking that race fuel with a higher octane could allow me to run more advance on boost?

Are there any guidelines or tips that you folk know of that could help with ign timing settings on boost + race fuel?

Is there a rule of thumb for using race fuel like the "1 degree of retard per 1psi of boost" which i have been working with so far ??

I'm not even sure which race fuel I should start with?


Perry

[stevieturbo]

You'll need to test on the dyno to have any way of quantifying.

Is the engine knock limited as it is ? Does it detonate when you try more timing, or can you keep adding timing to the point it simply stops making power ?

Q16 or something like that seems to be top dog, but the VP109's etc are also very popular.

That said, I know lots of people who simply add 20% methanol to their SUL, and say it offers similar performance to the much more expensive race fuel.

[stevieturbo]

Is there a rule of thumb for using race fuel like the "1 degree of retard per 1psi of boost" which i have been working with so far ??

And there is no such rule. The only correct way is through testing, not guessing.

Timing will be governed by so many factors that applying a generic rule is just blind guessing.

What sort of compression ratio are you at ?

[mgbv8]

You'll need to test on the dyno to have any way of quantifying.

Is the engine knock limited as it is ? Does it detonate when you try more timing, or can you keep adding timing to the point it simply stops making power ?

Q16 or something like that seems to be top dog, but the VP109's etc are also very popular.

That said, I know lots of people who simply add 20% methanol to their SUL, and say it offers similar performance to the much more expensive race fuel.

The engine does not have any knock sensors Stevie. Its too loud on open pipes to hear any knocking. I've only done the 1 degree per 1psi of boost so far.

[mgbv8]

Is there a rule of thumb for using race fuel like the "1 degree of retard per 1psi of boost" which i have been working with so far ??

And there is no such rule. The only correct way is through testing, not guessing.

Timing will be governed by so many factors that applying a generic rule is just blind guessing.

What sort of compression ratio are you at ?

CR is 10:1 Stevie !

[stevieturbo]

I assume you're tuning on a dyno ?

If so, the operator should be using "det cans" as they are commonly called, so listening for detonation is quite easy.

10:1 is pretty high, although boost used may not be. This will govern how much retard you really need vs boost/fuel etc.

Sounds like race fuel or methanol does have the potential for good results though.

det cans- basically a stethoscope.

http://www.scoobypedia.co.uk/index.php/ ... OwnDetCans

Now...these can be as simple as the above. Bolt the copper tube to the block and listen.
Or there are many fancy electronic versions, or cheap ones. These tend to pick up a lot more background noise though, so can be harder to filter them out. Some more expensive ones try and do this electronically so detonation is easier to hear.

But I find the cheap DIY ones work very well. The only caveat, is that you really need to know what you're listening for. The onset of detonation is just a very dull splat/tick noise when it occurs. The human ear/brain is an exceptional filter when you know what to listen for.
I also find the DIY version has less background noise, but the actual sound of detonation is quieter.

But on my own car when Ive tried, Ive heard it long before an electronic version has detected it.
On the likes of your car, with a big blower etc attached, the DIY version IMO would be better.

I could never get an electronic knock detector to work well on mine, although I'm sure there are some that would work well.

You can listen whilst driving on the street....but it can take a lot of concentration, so there are safety issues there. The better the ear defenders you use to make them, the more external noise is eliminated, so the better they will be.
On a dyno when doing a pull, that's no problem.

[Eliot]

Ive seen and heard the mgb on the dyno and and i can confirm that it is extremely loud - almost as loud as running with no headers at-all.

[stevieturbo]

Ive seen and heard the mgb on the dyno and and i can confirm that it is extremely loud - almost as loud as running with no headers at-all.

Buy good quality ear defenders then

With good ones, it pretty much does eliminate all background noise. It's eerily silent.

Although the electronic versions like Knock Box, Phormula etc, the noise you hear at your ears is generally a lot louder, as you now have volume control. I just think it's a little bit harder with them to identify detonation than it is with the cheap hosepipe method.
But if external noise cannot be isolated sufficiently, then they would be the better option.

But...I would be hugely concerned about using any dyno tuner tuning a vehicle who isnt routinely listening for detonation in the first place.

[daxtojeiro]

I agree, the det cans are a superb tool for ensuring your engine isnt detonating. I have also recorded the knock sensor output using a laptop, then played it back using free spectrum analiser software, looking for knock.

In my opinion a spark table should always take into account air temp when your boosted, this makes a massive differnece to how much advance you can run safely. Personally I owuldnt run a boosted engine without a proper 3D mappable setup which takes into account air temp.
This is my advance map from a 10.4:1 cr 5.4L RV8, no dizzy could achieve this:



and the Air Temp compensation, this is a bit drastic, but I dont want it to knock!

[stevieturbo]

Pulling 10 degrees ? I'd be concerned about cooking the pistons with that much !!

Too much retard is just as dangerous as too much timing.

Detonation will kill in a split second, too much retard will cook the pistons etc in a few seconds

I wouldnt be retarding the timing excessively and definitely not so much within such a small temperature window.

If the engine does indeed become so prone to detonation at those temperatures, I'd look into using another safety feature, like restricted rpm or something. Not by retarding the timing by that much.
Although the only saving grace in this instance is you are aware of the timing drop, you should feel it and be aware there is a problem, so you'd manually lift off.

IMO once total timing is getting below 10deg at full load...It isnt an ideal scenario. If you're below 5deg, I'd have huge concerns about engine longeivity. It might be ok for short blasts, but if you were to maintain WOT for any length of time, you do risk destruction, as chamber temps and EGT's will soar.

[daxtojeiro]

The temp will never get that high, well if it does Im going to know about it

In the real world Ive seen just over 40C, but the graph has to go on after that, so I removed a load so I would feel it.
Theres a warning light that comes on above 38C and I now have water injection too, so it will never get to 10deg of retard, if it did the engine would have stopped by then
thanks
Phil