HKS GTRS optimal boost level

[Reedy]

I got a GTRS installed a month ago and got 255rwkw at 1.2 bar still had standard air flow meter and am getting Z32 tuned this weekend.

My mods are are Full 3 inch exshaust, FMIC, PFC with boost controller, nismo 555cc injectors, exhaust cam, lightened flywheel and ceramic clutch, spitfire coils and bosch 044 fuel pump.

I was wondering is 1.2 bar the max optimal boost level for a gtrs or should I get them to put the boost level maybe 1.4-1.5 bar and will the turbo still be in its efficient range? I believe I need a new head gasket to lower the compression ratio and maybe some forged pistons if i do?

[600hp]

around 1.5 bar.

[Busky2k]

I would have said 1.5bar on an SR20DET but I would say there wouldnt be alot of gains going over 1.2bar on an RB25DET, especially if the internals are still stock!!

[Yorik]

Get the flow map and check, it isn't ahrd to do and there is an excellent how to on this very website on how to read flow maps.. Get to it!!!

[Andi]

Thought I'd save some bandwidth and revive this thread instead of making a new one. Thread Revival FTW!

From research it seems that the HKS GT-RS has the exact same specifcations as the Garrett GT2871R 52T Compressor. If thats the case and assuming that the Skyline version has the same compressor but a custom 0.64 T3 turbine housing, then would someone now be able to tell me the optimal boost range of the GT-RS if I've got the compressor map?

Well here it is. I'd just like to know what kind of boost I should run when I get the car onto the dyno for a tune.

[Al]

Get the flow map and check, it isn't ahrd to do and there is an excellent how to on this very website on how to read flow maps.. Get to it!!!

Just had a look at that flow chart and it doesn't mean shit to me. So from that graph how can you determine what boost pressure, on an rb25, the turbo goes out of it's efficency range. Can you answer that question? As that is what is being asked. If not it's best to just keep such useless comments to yourself.

Just because you know how to read it, doesn't mean everyone can. Just like the fact i know other shit that you wouldn't know .

[Al]

From my own experience with the GTRS, i would say about 1.3 bar, with a top quality tune.

[SilverECR33]

and this is within its Efficiency Scope. But what can the turbo be pushed too, say for Quarter Mile runs, without failing.

[Birnie]

I don't think the turbo will fail.

Just that if you keep pushing, you won't get any gain and the turbo is considered to be choked up and out of it's efficiency if that makes sense.

So yeah, i don't think wheels will start spinning off like the standard if that;s what you mean.

Edited May 24, 2007 by Birnie

[SilverECR33]

So your saying I could boost the GT-RS up to 28 PSI if i wanted, and it would make it.. ???

but What is the Tip of the Iceberg in relations to how high can I boost it till it *Chokes*?? or doesnt make more power.

Edited May 24, 2007 by silverbulletR33

[paulr33]

once you go out of the compressors efficiency you just dial in more heat

more heat = engine go bang

so running 1.3 bar may give you say 100 units of air at 70deg air temp

running 1.9 bar may give you say 110 units of air at 140deg air temp

bad numbers, but you get the idea

[BOOSTD]

There would be 20-30hp to be had from a 1.2-1.5bar increase. Maybe 50hp at 1.7bar, but after that efficientcy runs out.

Matt in japan =)

[SilverECR33]

ahh nice thanks , it was interesting because, There has been a few examples of RB25's with stock internals pushing 300rwkw with the GT-RS and i was wondering how far out of its efficiency it is, + how much extra heat.

[Al]

ahh nice thanks , it was interesting because, There has been a few examples of RB25's with stock internals pushing 300rwkw with the GT-RS and i was wondering how far out of its efficiency it is, + how much extra heat.

Different dynos. Some dynos are very power happy, or maybe the operator didn't set it up correctly.

Don't take the 300rwkw as gospal, otherwise you are setting yourself up for disappointment . Aim for 250-270rwkw; once again Dyno dependant.

[SilverECR33]

ahh well, It was a nice thought. I guess ill just stick with my current Proposed plan .. GT30R

[croat]

1.5 bar? 600hp you obviously have no idea. I had this turbo previously and there is not too much point boosting it over 1.3 bar. you will make some more power over that but very little.

[djr81]

There are three things you need to look at on the chart - two are important the other less so.

The FIRST IMPORTANT thing to be looking at is the amount of air (in lbs/min) the turbo will flow. It is this number that determines how much power your car will put out. There is a very strong relationship (largely independent of A/F ratios) between the air flow & the engine output. I am not going to quote a number (You can search & find it elsewhere).

The second important thing is the compressor efficiency. This is a measure of how much heat (ie wasted energy) the compressor puts into the air & therefore theat the I/C needs to remove. The good news is that high 70's are good number & that the islands are pretty flat - typical of a Garret turbo.

The less important number is the pressure ratio of the compressor. As the name suggests this is the ratio of the outlet pressure (ie heading toward to I/C) compared to the inlet pressure (ie just after the AFM's) This turbo can flow a ratio of 3. This is not the same as 2 bar boost (+1 atmosphere) and you will see much less at the MAP sensor.

Remember boost is only a measure of the failure of your induction system to allow air to the engine without restriction. It is nothing to brag about.