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turbo housing choice

sweetr33

By sweetr33,
in Engines & Forced Induction

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sweetr33 Experienced

sweetr33

Posted
Posted

Hi all, over the long buld of my engine and accesories i have come to a part where i am not that familiar with and would like some advice, the topic in question is turbo housings sizes.

I am getting a gt35r, power target of at least 300kw at wheels, what would be the top end and lag differences between a .82 rear housing and a 1.06 housing? I am told a .82 housing will be sufficient for that pwer target can anyone tell me of results or there oppinons about the housing choice and possible outcome?

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Cubes Grand Master

Cubes

Posted
Posted

.82

Peak power isn't everything. Its the area under the curve that is important.

I'm using the same turbo for my 3ltr.

On the 3ltr the GT35R .82 will only 'just' make 1bar by ~3600rpm, with the 2.6ltr, throw on another 500rpm spool time.

By 4500rpm it should be hauling arse.

Just as a comparison, the GT35R .63 flows the same amount of exhaust gas as the .82 GT30R. This is according to the turbine maps.

Cubes Grand Master

Cubes

Posted
Posted
Squish on turbo motors is overrated !!.... :flamed:

When building a motor you build it to make the most power it can everywhere in the rpm range.

Especially on a turbo motor, you want all the bottom end torque you can get.

Why take a step backwards and open up the squish that Nissan have already setup so well. :flamed:

When you are off boost you want economy, put the foot down and you want the burn to be as complete as possible to get that big turbo up and spooling.

All of which quench come in to play.

If its 10hp well its 10hp.

If its another 40km's per tank well its another 40km's per tank. ;)

Cubes Grand Master

Cubes

Posted
Posted

I think it would be very streetable. :(

I'm considering a .62/.63 what ever it is for the rb30det depending how the .82 feels on the road.

Generally the smaller the exhaust a/r the harder it hits, so you loose a little bit of throttle control.

MattSR Community Regular

MattSR

Posted
Posted

I agree with that statement cubes - for this reason I would just go for the 1.06 and be done with it..

Just for interest, did you know that Honda developed 3 different turbine A/R's for Ayrton Senna and Alain Prost in the 87/88 season one small, one medium, and one large. The engineers assumed that the slow speed circuits would easier with the small A/R, and high speed circuits would be faster with the large..

After several tests, Senna found the car was more progressive and easier to drive in all situations with the large A/R, so they ran with it at every race and shelved the small and medium housings.

Cheers,

Matt

discopotato03 Grand Master

discopotato03

Posted
Posted

Should be interesting to see the real world results . Theory suggests that a .63ARR housing would mean that the GT35R is a little big , and as the turbine maps show mass flow drops with the ARR number . There comes a point where exhaust restriction overrules the advantage of high compressor flow capacity and a step down in turbo size with larger ARR housings may work better . It may be worth looking into lower ARR compressor covers to lower the boost threshold rather than the smallest available turbine housing . The Garrett engineers reckon the mid sized housings are where maximum efficiency is .

I don't deny that I'm a bit fanatical about turbine inlet (back) pressure as it has so much potential to limit power and damage things - pistons mainly . The GT35R is really a Garrett hybrid of 35 series compressor with 40 series turbine , if the strait GT40R was scaled down the compressor would be smaller than the GT35R's .

I've been trying to find out if the GT BB turbos can be rebuilt and or custom built , sort of like a GT35 turbine with a GT37 compressor . Its debatable if that compressor could feed an RB30DET at higher revs and boost but the turbine/housing would not choke it .

I hate to say it but Ford may struck the righ balance with the large turbine housing and smaller E type cover on the GT35R .

While I'm here I keep hearing whispers of new turbos and gated turbine housings from Garrett in the near future , anyone know what to expect ?

It'll be a while before I get to this stage , cheers A .

Cubes Grand Master

Cubes

Posted
Posted

I always find your posts interesting discopotato. :D

Smaller exhaust a/r = less VE.

I see where are coming from where you say that a ford style setup (large exhaust a/r, smaller comp cover) may indeed give better results.

What turbine does the ford run? The GT35R turbine is huge, as big as a coke can.

The reason I ask that is if they run a GT40 turbine how do they get it all to fit?! ;)

dangerous_daveo Grand Master

dangerous_daveo

Posted
Posted

Shane, gemini ron had a "even" turbo, as in front and rear were identical, and you know what that car was like. He's since had it flowed and got a new wheel etc put in it, so its effective size now is apparently a t60 or so. And it aint made anymore power from that (which it should have, more air being forced thru, and should be cooler). So Id look at having it balanced like he orginally had.

discopotato03 Grand Master

discopotato03

Posted
Posted

The turbo on the XR6 is the same CHRA as Garretts GT3540R , the turbine is 68mm dia and the compressor is 82mm . Its turbine is a GT35 series not GT40 .

I have to agree about the size of its turbine - massive . While the GT30R's turbine is 60mm and probably a tad small I don't know of an in between size , maybe theres one coming . It makes me wonder how the VLT got away with a 60 mm T3 turbine though they supposedly had boost from 1500rpm ? I was told the state of tune was very low ie 7.8 CR and only 4-5 pounds of boost with no intercooler . I'll look into GT40R's and let you know the turbine details .

Cheers A .

discopotato03 Grand Master

discopotato03

Posted
Posted

The GT40R uses a 77mm (3") 78 trim turbine in a .95 or 1.06 ARR turbine housing - huge got bigger . The compressor wheel is an 88mm (3 1/2") 52 trim in a .58 ARR compressor cover . From what I can find GT40 compressors can be 82 or 88mm .

Ever noticed how some of the later GT BB's are closer in wheel diameters ie GT28RS (54 and 60mm) , GT3071R (60 and 71mm) , GT40R (77 and 88mm) . A theoretical GT3537R or 3576R depending on whose terminology you prefer sort of follows the same trend (68 and 76mm) .

Also HKS spec turbos , when they knew the difference in compressor to turbine diameters was large they chose smaller trim compressors ie GT2540 - 46 trim , GT3040 - 50 trim . Extra airflow and an attempt not to overtax turbine shaft power .

Compressor choise absolutely affects a turbines efficiency which affects backpressure and volumetric efficiency .

High volumetric efficiency is probably difficult to achieve on a turbo engine given that the turbine , no matter how good , is at best a minor exhaust restriction . My understanding of high VE is where careful tuning of the inlet system gives a ram charge effect which overcharges the cylinder and gives very effective scavaging on the valve overlap period . Careful exhaust tuning can be use to create and area of low presure at the exhaust valve which also assists scavaging and cylinder charging . Turbos with a better ratio of compressor to turbine stand the best chance of allowing higher VE than the poorer spec ones . This broadly assumes the wheels are efficient to start with and the housings are appropriately sized .

Just for laughs I scaled down the dimensions of a GT40R to that of a GT35R's turbine diamater and the 40R's ratio puts the compressor diameter at 77.71mm . This is a crude way to look at it but its a tad bigger than the GT37 compressor wheel (76.2mm) by 1.5mm but smaller by 4.29mm than the GT3540R's 82mm GT40 compressor wheel .

Cheers A .

discopotato03 Grand Master

discopotato03

Posted
Posted

Actually the correct OD for the VL's T3 turbine is 58.9mm , same as FJ20 and Z18's .

Nissan got the CHRA's from Garrett and cast their own housings for them which is why the comp covers often have Nissan Motor cast into them . Don't confuse these with the later ceramic BB turbos whose cores were made by Hitachi and whos only resemblence to the T3 is the exhaust mounting flange .

Cheers A .

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