Rb25Det Neo Intake Temperature Probe

[DaveB]

Hi all,

I'm trying to locate some intake temp graphs for RB25's to see what they *should* be at the intercooler output.

I am making about 217kw and I have an intake temp graph from the dyno which shows the intake reaching 58deg C near max power/revs. The tuner suggested 48 degrees would be closer to the desired temperature. The car is running I think about 8 degrees less timing than standard up top and I am wondering whether the high intake temps may be a contributing factor.

So I am trying to get an idea of whether 58 degrees is high for ~220kw; can anyone shed some light?

PS I suppose it would help to mention that ambient temperature on the day was 26 degrees C

cheers

DaveB

Edited December 10, 2012 by DaveB

[hypergear]

What sort of cooler are you running? on stock induction pipe and air box? Mine was in average of 35~40 degrees, depending on how hot the day is. Also if a restriction cause the turbocharger working hard then it can also make it hot.

[DaveB]

Interesting. Stock air box, stock intake pipe apart from the cooler which is air to water cooler with 3" in and out.

The tuner measured about 5 or 6psi of exhaust back pressure I believe, which he thought was a little high but reasonable. The exhaust is completely straight-through 3", so we slightly suspect the metal cat as being too restrictive (3.5-4" body) or else an undersized turbo exhaust housing (GCG high-flow of the stock NEO turbo).

[ARTZ]

My skyline with stock airbox runs 30-40 and as low as 25 with a cheap ass cooler mounted next to the radiator...weird huh...

It might be hotter on hot days i haven't checked..but its usually just over ambient by 5-10 degree...my cat was the same size as yours too

while my bt50 ute runs anywhere from 50-70 all day everyday

I had one of those GCG hiflows before and i swear it used to get hot too..it was making about 240kws at 19psi... i assume yours is auto though..

I wasn't measuring temps but it just felt sloppy after some spirited driving like the intake charge was getting too hot and I blamed the turbine housing..

I had a 21u housing not op6...not sure which you have,..what intercooler do you have??

[hypergear]

You will need to use a 3inch metal induction pipe and a pod for that sort of turbo. Factory injection pipe aren't big enough to flow that much of air. You will find a big jump in power figure.

[ARTZ]

oh just read air to water cooler...any reason for that setup...got any pics of it...just for interests sake

[DaveB]

Thanks Stao

Artz my housing is OP6 and car is auto as well (series 2 stagea). Cooler is a water to air 500hp unit.

[DaveB]

Lol main idea was to keep intake pipes to stock length and keep response up; theoretically the A2W setup can extract a lot more heat than a standard inter cooler but in practice not so sure... I'll look for some pics of the installation... it took so damned long I was just happy when it was working and I could hear the extra flow

[ARTZ]

yeah I think those hiflows are usually only good for 250 in ideal conditions anyway, maybe a little more with OP6...so in an auto 230 is about all I would expect...

I dont think you are too far off target...temps do seem high though...

how much boost are you running?

[DaveB]

Running about 16psi at 6,000rpm falls back to about 15psi at 6800. I am considering a turbo upgrade... but I plan to get the car tuned for E85 so I might just stick with this turbo for now (heck it's only ~50,000km old). Although the GCG issues of poor boost control and tricky oil seal at idle are still plaguing me.

[GTSBoy]

My guess is the stock intake pipe is sucking closed, causing vacuum in the compressor inlet. The compressor then has to compress the air from something negative up to your running boost level, which is a greater P2/P1 ratio than you would have if there was no suck shutness. Bigger ratio = more heat. Also, it means more shaft power required to compress the air, which means more power extracted from exhaust gas, which translates to less wastegate opening, higher exhaust manifold pressure which means you make less power from the same boost and can run less timing too.

W2A coolers are pretty good at absorbing a boost run's worth of heat.....right up until they heat soak. Then they take a while to shed that heat out via their radiator. Once you start heating the water in teh core up past a certain level, you will have to see it in the intake temps. This may play a part also.

Edited December 10, 2012 by GTSBoy

[DaveB]

That seems to match what I've seen so far - the cooler does seem to heat-soak badly. On a previous tune (RWD dyno) the car would make 250rwkw on one run, then on the next it would hit R&R and blow tons of black smoke and make 200... it was odd.

I have replaced the stock intake pipe with a stiffer silicone pipe from Just Jap; do you think this would suck closed under (this level of) boost?

Edited December 10, 2012 by DaveB

[hypergear]

The run that appears from R&R could be the induction pipe squashed shut / half shut. The hard silicon hose would stops it from shutting. From memory there is a customer made 255rwkws using it. 3inch induction would still be much preferred. PM M35scotty he makes bolton 3inch induction pipes for Rb25dets at reasonable price.

[DaveB]

Cool, cheers Stao

[STATUS]

common, had 4 GTRS in before i left for the usa and they were all between 48-54 degrees in the plenum, if you measure ex cooler like on R34 GTR expect 30-36

[GTSBoy]

Where was the temp probe for this dyno run mounted though? There's no plenum mounted temp sensor on an RB25. Did they just slip the probe under a hose clamp on a cooler pipe?

[DaveB]

That's what I've been wondering. Where have other people mounted theirs - plenum/intake manifold or intercooler outlet?

[ARTZ]

Mines tapped in just before throttle body

[DaveB]

found out that the probe was inserted into a vacuum connection on the manifold...

[DaveB]

Thanks Status, I was hoping that I had found the cause of my pinging troubles, now not so sure...