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Intake Air Temps - Max threshold?

25GTV

By 25GTV,
in Engines & Forced Induction

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25GTV Experienced

25GTV

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Posted

Hi guys, 

I have a r34 neo with a highflowed op6, E85, 3inch striaght through and a blitz rtn flow cooler.  Platinum Pro ecu.

Its a track drift car only.  Around 245rwkw on 16psi but it tapers off boost in the top end.

I monitor the coolant and oil temps now but I drift it in 2nd and 3rd gear for about 8 corners in a row with a tiny cool down on a 0.5km straight in between laps.  The cooler does get some heat soak.

I specifically want to know what sort of intake temps are acceptable and what would be a temp to stop and cool down the car at? 

Is there a general temp for this motor and fuel that means knock is imminent? 

Has anyone logged their intake air temps at the track with hard driving?

Had a good 2hr search before posting this.  Thanks in advance.

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GTSBoy Grand Master

GTSBoy

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It's an impossible question to answer. If you open the scope up to all engines and fuel types, the range of acceptable air temps is really wide. If you restrict yourself to just talking about RB25DETs, it's probably still too wide a range to be helpful. It will really depend on the state of tune of the engine and how close it is to wanting to ping. A relaxed tune will obviously accept just that bit more temperature than one that doesn't have any spare ignition timing lying around.

In your case, E85 is probably the really big factor though. It has such massive cooling power that, so long as you're not tuned to the ragged edge, it will probably allow you to completely heat soak the intercooler. Now, 16 psi is over a bar and if you compress air to a bar with only ~75% efficiency you can easily get >>100°C. So we'll assume that your hot air temp is well north of 100°. The intercooler will still take some of that temperature away even once it is soaked, but I'd be willing to bet you could run around 90°C post that cooler. The E85 should be able to cover you for that. If you were paranoid, you could look to add a little bit more fuel into the maps around your "drifting" load points to help that.

If it were me, wanting to stick with the return flow and the compromises inherent in that, and worried about heat soak, I'd look at a water spray for the cooler. Use a Bosch windscreen washer pump, a fine atomising nozzle or two and a reservior with a few litres capacity, and you should be fine for quite a few laps of drifting with a bunch of extra safety added.

But......if I had to pick a number that I wouldn't want to be thrashing an engine at.....then maybe 60°C. Something like that.

25GTV Experienced

25GTV

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  • Author
Posted

Thanks! I understand how broard the question is but was hoping for some experiended guys to provide a rough guide.  eg the 60 deg said above is a good rough place to start. 

I agree the e85 is the safety factor here as far as knock goes and on paper the hotter temp should mean lower density and less fuel required for that volume of air. 

Really, it should be rich when the temps get high.

 

I'm going to fit a sensor now and see what they look like after a few hard laps.  All I know is it appears to lose a little power and the temp on each side of the cooler becomes even after lots of laps.

Dose Pipe Sutututu Grand Master

Dose Pipe Sutututu

Posted
Posted

Get your IAT wired in, setup your EBC DC vs IAT compensation table happy days.

I don't understand why some tuners don't think IAT is important..... I know of a shop who has sent a few cars out without IATs.

GTSBoy Grand Master

GTSBoy

Posted
Posted
39 minutes ago, 25GTV said:

Didn't have an IAT stock and I haven't fitted one yet.

Yeah, that's pretty bad. The difference in density between ~15°C inlet air you might get on a really cold day (at boost, after the intercooler) and a heat soaked maybe 100°C situation is very large. Like 30%! At least it will result in your mixtures going super fat (assuming it was tuned at low temperatures), which is on the safe side. But if it was tuned on the dyno and the air was quite warm at the time, you could be exposed to going lean when you run it in cold conditions.

But the main thing is that the ECU would want to be pulling quite a bit of timing out of it in response to the hot IATs, and without a sensor, it just can't. In this case again, E85 is going to be part of your safety blanket. The rich(er, at higher IATs) mixtures also.

25GTV Experienced

25GTV

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21 minutes ago, Dose Pipe Sutututu said:

Just make sure the IAT is post cooler, pretty useless before cooler or at the turbo inlet.

 

I will, being the std manifold its hard to get it somewhere that heat soak front the hotside wont affect it. I might try just before the throttle body.

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