Tuning

[Novice1]

Just wondering what is the recommended air/fuel ratio for a turbo NB.
Have changed plugs twice in two months, as black as. Have changed to colder plug. Thinking retune time. Only changes recently coolant reroute system fitted.
Secondly, how much boost can one run safely on stock internals.
Only clutch has been built up to 1400lb pressure plate, 780lb standard.
I, have heard 14psi is safe, but value others opinions.
Currently, running 12psi, 168kw atw.
Cheers Novice1

[blackster]

AFR = can of worms

AFR is adjusted depending on the amount of timming and boost your running in order to prevent detonation. However in saying that AFR is not a single entity that primarily prevents detonation.

12.5.1 for turbo applications seem's to yield the most power, however if your planning on tracking the car with a stock bottom end, I would be going richer than that. If your asking about breaking point, it basically comes down to reducing heat for NBs.

I pulled my plugs out not long ago (range 7) they were in for about 1.5 yrs and replaced them, they had very little soot/carbon build up. 170rwkw @ AFR 11.8. The car hasnt hit the track yet, I have another map that's 158rwkw @ AFR of 11.1 with a bit less timming, thats the map I plan to use for track.

Hopefully some of racers will chime in and give there opinion about set ups on there car.

[Novice1]

Thanks Blackster:

Changed the plugs from a 5 to a 6. Still as black as soot. Will change to a colder plug, 7.
The car despite the blacked up plugs is running very well.
Not quite sure what as altered the engine running rich.
Had coolant bypass, undertray, radiator shrouded.
The engine is certainly running a lot colder.
Hesitant re retune as damn expensive, but don't like the engine running so rich.
Cheers Novice1

[Phil @ P5]

Black plugs are not uncommon, and don't really tell you much of a story. For the amount of time you're on boost compared to cruising/idling/driving around town is small. Get an AFR gauge in there and see where you're rich, rather than trying to second-guess.

Phil

[Novice1]

Thanks Phil:
At $150/hour dyno time, tuning I will check out the AFR gauge this weekend.
CHeers Novice1 aka Ron

[zoomzoom]

AFR guage is useless unless you have a wideband. If you really want to keep an eye on it yourself you can get wideband units but they are not terribly cheap. I have the innovate motorsports one for my megasquirt, but others have also used the AEM I think and there are also others out there.

Also changing the plugs to the colder 7s will only make them blacker if anything, but it doesn't make much of a difference. The cooler plugs are more just to keep down in cylinder temps before combustion to minimise chances of pre-ignition.

Tim

[Novice1]

Thanks Tim:
At the moment I am still trying to sort out why my car is running rich, plus trying to get round the tuner who password protected fuelling maps on my car without my consent.
Cheers Novice1

[Benny]

If you run more than 8lbs of boost, your rods will bend.
The pistons are OK, as is the crank, but the rods are the weak link.

You may not notice your rods are bent, until one breaks, and it isnt easy to check, but even standard SP's, running at 8lbs, all have bent rods by now.

Isn't that right, Big Dog?

[Sean]

I've run plugs in the 9 heat range with success (and higher boost). Plugs are cheap and if the car runs well I wouldnt worry about them being a tad dark.

Remember too that although most guys will tell you 12.5 is optimal, you might find that a tad more fuel will allow you to run more timing advance which may ultimately give you better power and fuel economy - I'm not saying it will, bit in many modern DOHC engines I've seen richer AFRs and a tad more timing yeild good results.

Just remeber, the best tune is the one that gets you to the other end of the track (or home) reliably, saving a few hp or a little bit of fuel, or a few dollars on plugs wont seem so important if it doesn't make it home.

[bigdog]

If you want to run more than 12 psi you need to accept that things can and probably will break. Around the 8-10psi range it is rare to see any problems, although a few SP owners have had bent rods, but I still think this has more to do with buzzing the rev limiter than anything else (not necessarily in the hands of the owners, more likely by service technicians on test drives).

My SP has been running 8.5psi @ 145 rwkw for the past 80000km with absolutely no problems apart from clutch slip, and on strip down last month the engine looks perfect, including the rods (straight as a die and zero wear on the crank). Dave's car has a hi/lo boost setting with 12psi on the high switch. At over 200000km (including being thrashed by journos from all over in its youth) and still brilliantly strong - you can't say anything negative about the reliability of the BP engine.

The engine I'm building now is going to see me through to the end of my SP's life, and has Eagle rods and Wiseco pistons to ensure longevity, even if I turn the wick up occasionally. The only reason I'm doing this is because it was convenient to do so, not because I needed to.

You can get away with higher boost settings, but it is a lottery, plenty of engines in the 12psi+ range have gone bang, so it's up to you...