Rb25 Neo Intake Temperature

[Shoujiki]

Hey guys, After a little advice on my intake temperatures.

Few months ago installed an MFD into my R34 GTT. I used the stock GTR sensors for Exhaust and Intake. Now my car has a Blitz Return flow FMIC. To install the intake temp sensor, I drilled a hole in the "return" pipe up near where it couples to the engine bay piping and mounted it there.

So tonight is about, 10 or so degrees outside. From cold start, the intake temp on the MFD reads about 15 or so. Driving around a bit, usually gets it up to about 25-35 degrees, depending on the situation. Tested with a little more throttle and if boosting for a while it got up to 80 or so degrees. That seems quite high to me.

Thinking about it, the turbo is sucking air in through the intake (stock airbox), "compressing it", running it out and through the I/C, and back to the throttle body. So i assume it's going to be hotter when on boost, as the turbo is hot, so it'll be heating the fresh air charge. But that hot? The air that the intake plenum is seeing is 80 degrees that means. Seems too high. What would cause such a high temp?

Cheers, Kurt

[GTSBoy]

Sounds like that intercooler is doing nothing at all.

[Shoujiki]

How is that possible? Could it have a restriction in it? It's a proper Blitz Return Flow. Any way to test for this? The system holds boost pressure well at 0.89bar. Controlled via Profec 2 Spec B.

[GTSBoy]

If you can, put a temp sensor in the pipe upstream the intercooler. In fact, make sure you haven't installed your existing temp sensor upstream the intercooler!! What turbo are you running, how much boost? Do you have a multimeter with a thermocouple, or access to some similar alternative temperature measurement device? If you do have something that can read thermocouples, then you can buy a few bare thermocouples from an industrial temp measurement company (there's a few around) for a few bucks and you can bodgily install them by putting them into the joins between intercooler pipes and the rubber hose joiners. With a bit of care they will work, although you do stand a chance of breaking them while putting it together or pulling it back apart. Useful for checking temps on a temporary basis.

What is the air flow situation around your intercooler? Any helpful ducting? Anything there that will interfere with ambient cross flow?

[scotty nm35]

Test the sensor reading using a cup of boiling water and a thermometer, I would say it is out.

[GTSBoy]

Valid point!

[R31Nismoid]

Also stock GTR sensors are so slow to react you'd never know what you were really seeing anyway. Should've used a decent sensor that'll actually give an accurate result.

[SargeRX8]

Could these sensors pickup the heat of the cooler piping it self? After a long drive almost any metal in and around the engine is untouchable.

[scotty nm35]

Yes, especially the GTR style solid screw in style of sensor. If you look at the aftermarket bosch style sensor it has vents and a small bulb which is isolated from the piping, this is what most people use for aftermarket intake air temp sensors on standalone computers.

[Shoujiki]

Thanks for the replies guys, really good info. GTSBoy, AFAICT there is no anomalies in the intercooler setup in terms of flow or restriction issues. It's a fairly standard type install, nothing out of the ordinary. The car runs great and doesn't feel doughy really at all.

I got the GTR sensor because I knew it would function with the MFD correctly. Easy enough to change, but i'd have to check up on the resistances and compare to see if the MFD could interpret it correctly.

The piping heat soak issue is a really valid point. After a long drive, you would indeed expect the surround metal to influence the value. The way I have this installed isn't exactly like the GTR, mines just in the pipe. The GTR has it on a flat boss section on the output of the cooler. So it could indeed be picking up soak from the metal.

[Rolls]

To be really sure you need to test the temperature pre intercooler and post intercooler, even if the value is wrong at least you'll see a percentage drop knowing everything is working.

If you can get a proper pt100 sensor and datalogger you can then see what the real temperature is, need to check the specs to see what the lag time is though, they might not respond fast enough to be accurate.

Edited August 20, 2013 by Rolls

[gotRICE?]

Im not sure heatsoak is your issue. Id say its the sensor.

Mine is mounted by the throttle body in my R33, so its sitting ontop of the engine and i never see anything near temps like that bar idling for long periods of time. And even then, bringing the revs up even in neutral will drop the temps by 30 degrees in a few seconds.

[R31Nismoid]

My stock 15yo GTR Intake sensor would hit 60 degrees in traffic and once clearing it onto a freeway or otherwise it would take 2-3mins to come back down under 50 degrees, horridly slow reaction time.

[Shoujiki]

Well that might be my issue then. You'd think Nissan could have made an accurate system to begin with! Only reason I got this sensor was because I knew it would interface with the MFD correctly. I wonder how installing an aftermarket sensor would go. Keep in mind that this is being displayed on an MFD, I wonder if the MFD itself is at partial fault in the way it interprets it? Really at the mercy of the electronics in this situation ai. As stated, the only way to really know is to install a proper accurate sensor and logger and check, at least to give an indication that it's "working as it should". I'd expect the engine to not being running correctly (detonation, doughy feel) with temps entering the intake that high.

[GTSBoy]

My stock 15yo GTR Intake sensor would hit 60 degrees in traffic and once clearing it onto a freeway or otherwise it would take 2-3mins to come back down under 50 degrees, horridly slow reaction time.

Yeah....but wasn't it installed in the plenum? That's bound to have a slow reaction time. Big heavy sensor screwed into large alloy heatsink.

In reality, the GTR's air temp sensor was probably only used for protecting the motor from severe heat events. I don't think there was any extra lookup table in the ECU for timing correction against temp, or any of the other usual uses. The RB26 ECU is not a lot different from the RB20 ECU.

[R31Nismoid]

Oh yeah for sure, just highlighting the point that even if there is colder air flowing over it, does not necessarily mean you actually get that reported.

And yes you are right, it's just a protection thing where timing is pulled IIRC in the PFC, or maybe that's water temp, i forget haha

[jrm]

Few months ago installed an MFD into my R34 GTT. I used the stock GTR sensors for Exhaust and Intake. Now my car has a Blitz Return flow FMIC. To install the intake temp sensor, I drilled a hole in the "return" pipe up near where it couples to the engine bay piping and mounted it there.

I haven't gotten around to installing that sensor for my MFD yet (I have a brand new sensor from Nissan waiting for install) because I haven't been sure where best to install it, or how to do it properly without air-leaks, etc. (Anyone with suggestions, feel free to let me know )

However, keep in mind this sensor and read-out on the MFD wasn't an 'intake temperature sensor' but an 'intercooler temperature sensor'. The sensor itself when factory fitted to the R34 GTR was actually plugged into a spot on the factory FMIC - I can't recall it if it was on the 'hot' side or the 'cooled' side, though (Perhaps someone here knows).

This may influence why you're getting different readings from those with a GTR, and the sensor itself could definitely be affected by heatsoak given the different position you have it installed.

[NATAS]

Intake of 80C degrees.... I can't really be 100% sure unless I physically go poking around with a multimeter at you sensor/s and poke around in your bay.. as well as how the rest of your hardware is setup.. However, it seems quite normal to me.... Back in 1st year aeronautical engineering at uni, we learnt in our physics classes that when a gas (in our case, the gas is air) is compressed, heat being generated is the result, the more the gas is compressed, the more heat is generated. The turbo itself being hot has very little to do with the heat being added to the intake temp, it's the actual physics that's taking place during the compression of the air. So the outside ambient temperature before the air filter only plays a small part in the overall intake temps and it any, only takes place before the turbo compressor.. After the compressor is a whole different ball game as there is an entire 1.5 inch thick text book about the physical behavior of gasses as well as thermo dynamics.

A few things can be done to help keep inlet temps down. Personally, I put in a whole heap of ideas I developed using the stuff I learnt at uni when putting my car together - http://www.skylinesaustralia.com/forums/topic/425426-what-do-you-guys-think/#entry6861236 I reduced the heat soak effect in the R33 that usually take place in the section of the intercooler pipe that goes over the top of the radiator by totally reversing the flow path between the turbo and the throttlebody, so that the pipe crosses over the radiator BEFORE the intercooler. Any heat soak caused by the radiator is removed by the intercooler before entering the throttlebody. I mean, what's the use of having an intercooler when the intake flow is heated up again by the radiator's heat soak before entering the throttlebody ??? I also added some fibreglass exhaust bandage to wrap up that section of the intercooler piping to reduce the heat soak even more.

Something I did which you can't see in my photos is I mounted a 10in thermo fan on the backside of the intercooler and have intercooler fan relay triggered by the speedo signal - the fan comes on when the speed drops below 80 km/hr (as the air-to-air intercooler effectively does not start working until the car is up to speed) and turns itself off when up to speed. Well, my FMIC is working AT ALL TIMES which helps the intake temps big time - especially when the engine is making power taking off from stationary.

The last thing - I installed a intercooler water mister (NOT SPRAYER) which is triggered by a Hobbs (pressure) switch, set to kick in at 5 psi before full boost.... You see on Youtube a lot of these water sprayer systems some people are using that gives them streams of water like pissing on the intercooler are in fact quite useless. More physics - the more surface area on water 'droplets' the more evaporative cooling effect takes place. The finer the droplets the more surface area there is. The nozzles I used are 0.2mm brass units with ball bearing anti-drip fittings designed for industrial evaporative cooling on big machines. This combined with a high pressure water pump (not the useless windscreen pump !) generates a extremely fine mist. I have 4x 0.2mm nozzles mounted around the bumper opening aiming away towards the front of the car. The water misting and intercooler fan gave me an additional 9kw at the rears. That'd be the cheapest 9 kw on the entire car considering the more powerful the car gets, the more expensive each additional kw becomes.

Edited January 22, 2014 by NATAS

[discopotato03]

I think you can safely assume that any temp sensor with a relatively speaking large thermal mass isn't going to be fast acting . I though GTRs used the same sensor for water temp ?

Anyway my GTS25T has the same Blitz intercooler and my air temp sensor is screwed into the back of the std cast crossover pipe . I never see anything like 80c unless its been shut down for a short time on warm days .

I'd say Nissans idea with GTRs was to have a sensor that told the computer that the system was hot because it had be running at full load for an extended period of time . From memory that sensor was in the plenum inlet on R32/33 GTRs and the intercooler outlet collector on R34 GTRs .

Also mass air sensors measure temperature because that affects density and therefore mass . Manufacturers can work out air temps , in a std car , by knowing what it is at the AFM . Std car std boost exhaust etc etc . That all goes out the window once you change things .

Ultimately we both need the air temp sensor , a real one in your case , mounted in something that doesn't have much thermal mass or parked right above the engine copping all the radiated heat .

A good spot would be in the IC return pipe far enough ahead of the turbo and exhaust manifold to not be influenced by them .

From memory Guilt Toy had his in the duct before the throttlebody but that had a non std inlet manifold and throttle on the cold side of the engine bay . Plazmaman one I think .

A .

[Shoujiki]

The response by NATAS was fairly epic lol, Thanks for taking the time to write all that up!

Forgot about this thread, but in any case, i found the issue a while back... the sensor is installed in the wrong pipe,. I've got it in the pipe that comes out of the turbo to the inlet of the cooler. Hence the temprature being higher and it going up whenever boost is reached.

My bad, but still works great and is quite accurate to the relative outside temperature at rest. So i use it more as a guide as to the intake temps. Be good to get another sensor maybe and put it in the outlet pipe, and have a switch to go between the two.