Air Intake Temps

[R33GTRKid]

Hey

I have been thinking with the discussions recently about my trap speeds not matching my dynoed power levels properly (380rwhp v 111MPH on a 12.3).

I have exposed M-pods with no shield or snorkel.

Recently I have been watching my hand controller and my average intake temps are about 50 degrees, however when I sit at the traffic lights for anything more than a few seconds, this goes up to about 55 degrees and takes a few minutes of driving for them to come back down again.

Given the long staging at the drags it is likely that my intake temps when the light went green were at least 55 degrees.

Is this hot? would this be robbing power?

If I enclose the pods using the methods on here, how do I get cold air into there? do people here modify the stock snorkel for it to push cold air into the enclosed area? What about the hole in the passenger side front guard where the stock airbox usually slots into, at the moment there is a black plastic thing that sits in the hole but it completely seals it?

I know on my front bar next to the passenger indicator in the lower section, the slotted black plastic has been removed but I cannot see where the air would flow to?

Any input re the best way to do this will be greatly appreciated as I have spent a shit load of money on the car and I want to perfect the set up before I spend more money on dyno time.

Thanks in advance fellas

Edited February 17, 2009 by R33GTRKid

[Adriano]

There is no need to push the cold air into the pods, if you seal them from the engine bay air, and allow a path of the cold air then the pods will draw it in themselves. What Front mount are you using? at 380rwkw i would be looking at upgrading from the stocker. 50deg intake temps are high unless you are living in darwin, is this when yopu are under load or cruising?

[Strik3r]

PFC air temp correction doesnt kick in till 70 degrees.

My intake temps are similar to yours - 45-50 degrees in summer. A lot of it depends on where your intake temp sensor is located as you can get a lot of heat radiating from the engine block. You have to be careful when shielding your pods. I have a shield up on the side between filter and block, but when i put a cover over the top as well, my intake temps actually go up by a few degrees (not enough air movement in the air box). I think its not a bad idea to have some sort of wall between your air filter and the engine, but aside from that, look at some ducting to run from somewhere in your front bar and up into your pod area. If its purefuly for track/drag use then consider removing your passenger side head light while you are at the event - thats a direct feed of cold air straight to your filter.

whats your engine setup ? Its possible you were on a happy dyno and aren't making as much power as you think ?? Also things like track conditions, tyres, etc. can effect your trap speed/time. Its also possible you've reached the limits of your intercooler. Check for pressu re differences on each side of the cooler, and also see if you can measure intake temps pre and post cooler to see how well a job its doing.

[Mr GTR-32]

Hi there,

I have a R32 GTR, your intake temp readings from your hand controller are the readings taken from the intake manifold sensor, its not the exact actual air temp from your cooler, i know this because i removed this sensor and tapped it further down into my aftermarket aluminium pipework as the air exists the cold side of the cooler before it starts to run up into the intake manifold and you will find that the actual air temps should be as per outside ambient temperature give or take 2 degree depending on wind chill factor and cooler heatsoak.

Yeah i initially thought shit how the hell are my intake temps so high i am running a 149mm tube and fin TRUST cooler but once i relocated it further down the real intake temps where registering and making sense now.

Although i dont know if what i have done is a bad thing but i have had my car tuned for over a year now with that done making 325Rwkw and my knock has never been over 20 and fuel economy is around 400klms per tank sensible driving

Shielding the pods should help greatly for the initial heat soak they get when sitting around at lights i am going to do this also, hope this helps relocating the sensor is handy to see how well your cooler is working but usually sits around ambient anyway i have had alot of time watching it on the good old hand controller, be more worried about your KNOCK levels thats what destroys engines.

[R33GTRKid]

yeah my knock never goes over 25 ever, actually 24 IIRC.

I might get the cooler pressure checked to see what it is doing, it is the standard 33 GTR one.

I am just trying to explain the difference between power and trap speed.

Factors slowing(/reducing power?) trap speed were 18 inch 265's, heading into a 13 knot head wind (direct head wind) and an ambient temp of about 30 degrees, 50%ish humidity.

[R31Nismoid]

Either way - as i found out, using the H/C as a guide is wrong with the stock sensor.

The temp sensor suffers from heatsoak from the plenum and if you watch from startup it slowly climbs for about 20mins until it hits 40-50 degree's depending on ambient temps.

Im looking to move the sensor to the intake piping or something for a proper reading.

So if your using the stock one, forget it for now.

As for a restriction (GTR core) if there was a restriction, that wouldnt alter the power reading or whatever as the motor only makes the power based on the air it is seeing.

So if your making 25psi @ the turbos, and only 18psi @ the motor and make 280rwkw... restriction or not you still make 280rwkw.

The intake temp will be a bit higher because of the restriction... but then GTR cores are tried and proven with 350rwkw+ so it wont be that unless the core has shat itself which would be a first.

[R33GTRKid]

the only other thing I can think of then is a boost leak - on the dyno it hits 17psi at about 4,200 and holds to about 5,000 then tapers down to 15 and holds steady.

At the drags I did not see any higher than 15.5 at all.

So if 17psi was the 283rwkw, I guess the lower PSI (possible boost leak after tune) then explain the 110MPH trap speed?

what is involved in a proper workshop boost leak test - I mean getting told 'it will take a couple of hours of looking around the pipes' does not seem to be a very scientific way of doing it - I though you blocked off the turbo intake pipes or something and then pressure test the system using some form of tool?

[blind_elk]

The sensor is where it is because the ECU needs to know the temperature of the air at the closest point to where it goes into the cylinder, so it can calculate properties of the air. If you move the sender to a cooler spot, then the ECU will be deceived about the air, and will incorrectly fuel the engine.

[R31Nismoid]

^^ i dont believe the air is actual that temperature.

EG:

On a night in the hills i read 35-40 degrees on the H/C readout (ambient is lets say... 10 degrees or so on a cold night up in the mountains, its probably less in reality)

I get out, pop the bonnet and touch the intake piping right near the plenum... and its cool to touch.

It would have to be sub 20 degree's right near the start of the plenum for it to be cool to the touch.

Now im not going to accept easily at all... that there is a temp increase of over 20 degrees from the start of the plenum to the throttle bodies.

Especially when the air is moving at a substancial speed like it is @ 5000-8000rpm

Also, if you add the Gizmo insulator gasket (or whatever part URAS was talking about in another thread), then the sensor temp will also drop same as moving the sensor... its just easier to move a sensor in my book

Its something the more i think about plays on my mind

[FineLine]

I have my sensor placed about 20 cm before the throttle body. 42 degrees is the most I've seen to date.

[R31Nismoid]

20cm would put it close to the cooler outlet?

What is the ambient when it was reading 42?

What is the ambient/What do you normally see Noel?

sorry for the lots of Q's

[FineLine]

20cm would put it close to the cooler outlet?

What is the ambient when it was reading 42?

What is the ambient/What do you normally see Noel?

sorry for the lots of Q's

No probs mate. Working from memory the ambient for 42 degrees was 33/34 degrees.

It usually runs around 35 degrees when the ambient is mid to late twentys.

Because of the piping setup I am running the sensor is a good 60 cm away from the cooler.

[Cjmartz2k]

Your "descrepency" in trap speed vs. hp has nothing to do with your air intake temperatures. You run what you run and you did it with what ever power your car is making. It has to do with some people's notions of what hp should be or what they have done on a dyno (aka "aussie hp"). There are a lot of people on here that tell you "your trap speeds don't match your hp figures" because the numbers they made on the dyno were lower for the same kind of trap speeds. It's just different dynos. Most dyno's around the world read higher than what a lot of dyno's in Australia read evidently, but maybe you found an "accurate" dyno. Don't let people tell you what your hp figures should be, especially when you have a dyno sheet and a time slip in your hand.

[Adriano]

IMO the factory Air temp sensor is a joke, it is the same sensor as the coolant temp sensor, so operating in air makes it about as responsive as an ocean liner, It doesn't effect fueling, only retards the timing above 70deg.

[shombre]

IMO the factory Air temp sensor is a joke, it is the same sensor as the coolant temp sensor, so operating in air makes it about as responsive as an ocean liner, It doesn't effect fueling, only retards the timing above 70deg.

Adriano, in MAP-sensor'd JZ-series engines, the PowerFC definitely has adjustable tables for fuelling vs inlet air temp. I imagine in MAF-driven cars this may be a non-issue, but I would have thought that for RB26s, there would be some form of compensation in the stock engine management for perceived inlet air temps ? The density of air at 10deg versus 30deg (for example) mandates this IMHO. Happy to be corrected, as I am not familiar with RB2x engines other than what I've learned over a few years of browsing this particularly excellent sub-forum

[R31Nismoid]

Your "descrepency" in trap speed vs. hp has nothing to do with your air intake temperatures. You run what you run and you did it with what ever power your car is making. It has to do with some people's notions of what hp should be or what they have done on a dyno (aka "aussie hp"). There are a lot of people on here that tell you "your trap speeds don't match your hp figures" because the numbers they made on the dyno were lower for the same kind of trap speeds. It's just different dynos. Most dyno's around the world read higher than what a lot of dyno's in Australia read evidently, but maybe you found an "accurate" dyno. Don't let people tell you what your hp figures should be, especially when you have a dyno sheet and a time slip in your hand.

Well considering everyone here is using the same brand of dyno

I think its very easy/correct to compare within a small margin... especially when the turbos being used, boost level etc should read "roughly" in the same ballpark as everyone else...

So if it is, and then its not running the MPH everyone else does... you tell me where the discrepancy now lies

[Adriano]

In map sensored ecu's, the air temp sensor in necessary to obtain the air density, however in an afm setup, the afm measures the mass of the air, so is self compensating for the air temp. Im willing to bet the soarers dont use the sam estyle of temp sensor as the rb26. One other major issue i have with comparing dyno figures to MPH is that even the calculators dont allow for the shape of the torque curve, wherby a meaty fat torque curve will certainly be faster than a peaky setup making the same peak power.

[rev210]

If the car sucks hotter air to begin with the power will be down relative to colder air.

There are other factors that will effect the tune also. Some of which the ecu can make automatic adjustments for but, within a range and assuming the tune is comprehensive.

I have tested a really ugly solution with the sheilded Vs unsheilded pods by using a cut up foam mat. The difference in temps at the intake are quite significant, as is the power.

You also have other temp related / heat soak issues to contend with including how hot fuel gets etc.

Simple things like fowled plugs can also contribute.

[shombre]

In map sensored ecu's, the air temp sensor in necessary to obtain the air density, however in an afm setup, the afm measures the mass of the air, so is self compensating for the air temp. Im willing to bet the soarers dont use the sam estyle of temp sensor as the rb26. One other major issue i have with comparing dyno figures to MPH is that even the calculators dont allow for the shape of the torque curve, wherby a meaty fat torque curve will certainly be faster than a peaky setup making the same peak power.

Correct, so we agree that MAF - by definition - doesn't need the IAT to estimate air density. Can you explain how the differences in temperature sensors, if that is actually the case, between engines matters ? On a speed density based system, inlet air temp is needed - is this not universal, irrespective of the temperature sensor type ? Does the stock RB26 only modify ignition advance or retard for various sensed air temperatures, or does it also alter fuelling ? If the latter, as I suspect is the case, then the type of sensor is not germane to the issue.

[Cjmartz2k]

Well considering everyone here is using the same brand of dyno

I think its very easy/correct to compare within a small margin... especially when the turbos being used, boost level etc should read "roughly" in the same ballpark as everyone else...

So if it is, and then its not running the MPH everyone else does... you tell me where the discrepancy now lies

I'm not stirring up the whole "aussie hp vs. BS american hp" debate, I'm just saying I don't think there is anything wrong with his car. Are you guys saying that judging by his trap speed vs his dyno sheet, he has a problem with his car?