Intake Air Temperature

Good morning.

Can someone tell the relation of power increase on reducting IAT?

In other words, what increase in power can I expect for every 1°C reduction?

Thanks

The air density will be about 0.003% greater for each 1degC reduction. I think the power change would be about .15% per degC, so a drop of 10 degC, could yield a 1.5% horsepower increase.

A little googling found this article with similar results:

https://buildingspeed.org/2012/04/23/temperature-and-horsepower/

Good article and conclusion David. I was thinking that the profit would be higher but it is still an important number. I am thinking of getting about a 20°c reduction in temperature using my iced watercooler compared to a conventional intercooler

Well then what it really might buy you is if the air temp increase was causing you to be knock limited. Then cooling the charge may allow better ignition timing, and a further increase in power.

I'm not worried about the knock since we're going with a maximum boost of 1.3bar and racing gasoline with 110 octane and 16.5% oxygenation. What I'm trying to do is scratch all the hp from the engine by improving the efficiency of the elements

As David said, the rule of thumb (it varies a little) I'm aware of is 1% per 6C. Because it's compounded, and not additive, it can make a bigger difference with bigger temperature variations - if you have, say, a 60C difference that isn't 10% more torque/power, but a (very) little more.

Is there a reason you're restricting yourself to that boost level - such as regulations?

Depending on the engine, you should see significant gains with a good rework of the ports and valves/valve seats, re-working of the manifolds to smooth the gas paths,etc - you shouldn't need to open them up much, if any, just make sure they're free flowing without sharp angles or crap.

You can probably increase the CR by skimming the head and/or block - if you find you can advance more than a couple of degrees past the MBT point without any detonation it means you can run more compression - how much will depend on testing.

Fit a vernier cam' pulley or sprocket and try adjusting the timing of the camshaft(s) a little one way or the other - but be careful of V2P interference - this could be checked any time you have the head off.

Good morning Gord.

Is not about the rules . It is because of the engine.

I don't know if you have read my previous posts but it is a 1000cm3 motorcycle engine mounted on a formula 3. Specifically it is a BMWS1000RR. The cylinder heads of motorcycles are much more advanced than the cylinder heads of cars, but even so, work has been done on it. The particular problem with this engine is that it only has 6mm of wall between cylinder and cylinder and it is likely that the head gasket could fail because of that. The cylinder stuuds have been changed from 8mm to 10mm diameter so I don't think that would cause any problems but the engine in general is not as robust as a car one. That's why I commented that with those low boost pressures and race gasoline I wasn't worried about the knock. It is about seeking maximum efficiency without forcing the engine more. In the end I am aware that to find the boost limit of this engine, it would have to be taken to the breaking point

Ah, I recall now, we had a bit of discussion about it. Was it a hillclimb car?

As you say, the engine will breath a LOT better than almost any auto' engine, so peak acceptable combustion pressures may be reached at lower "boost" pressures than may be required in those.

6mm is actually good for bore to bore clearance, much more than, say, siamesed auto' cylinders - however, 100% agree that it's better not to push it unless you've the budget to throw away the mistakes.

Exactly. It's a hillclimb car. I really can't afford to break engines to find limits. We are going to go in safe values and advancing little by little. I will tell you the results I get.

If you haven't done so, I'd suggest keeping an eye out for any engines that come up at a reasonably price - even complete bikes you con on-sell un-needed parts from. Having one or two spares (or a collection) can be a huge time saver if there is a problem and you then have to track down a replacement and then make any required mod's for the application.

I have a replacement motor and a bunch of parts but that's not all. Specific connecting rods and pistons are required for the turbo application.

We'll see how the set works. To this day I don't know of any BMWS1000RR turbo engine fitted to any racing car and we don't know what results it will have. Only the suzuki gsxr in turbo version are known. The only consolation we have left is that in the atmospheric version the BMWS1000RR is the best and hardest engine today. Let's hope that says so.

In a couple of weeks we hope to do a dyno test. One of the things that a well-known garrett turbo supplier is telling us is that we could have losses on the power at high RPM with the AR.49 turbine that we have opted for and because of the backpressure that this could produce. This combination was chosen to have a fast spool.

Until the day of the dyno it will not be known.