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Modifying Turbo

Cool Hand Luke
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discopotato03 Grand Master

discopotato03

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No worries Biz , actually I stuffed up earlier on and was thinking RB20 .

The real GT3071R is shown on the turbobygarrett site , you need to have a look at the turbo comparison sheet by clicking on the lower RHS of the small or medium or large frame turbo list boxes . Its the last of three and the table quotes 450Hp compared to 420 for the two victim versions .

I looked at the maps for 71mm 56T in .50AR TO4E cover (GT3071R) and 76mm 56T in .60AR TO4E cover (GT3076R/GT30R) . While the maximum or choke flow is not too different the compressor speed lines are .

The GT30R gets to ~ 50lbs air at approx 60% efficiency and a little over 115,000 rpm and 1 bar boost . The GT3071R just gets there at 2.2 bar (positive) and up around 145,000 rpm .

So you can see that the 3071R is really spinning its tits off at twice the positive pressure to move the air .

To me it seems that the 71mm or GT35 compressor is at its end in the TO4E series comp cover which was originally intended for 76mm compressors . The 76mm or GT37 compressor (GT30R/GT3076R/GT3037) would probably do a similar thing if used in a TO4S cover designed for 76 and 82mm wheels .

Its difficult to make a direct comparison of the GT30R and GT3071R because they give different results based on comp diametre , trim size and comp cover series and AR ratio .

The best results I've heard of on an SR20 was using a HKS GT3037 in 52 compressor trim/.50AR TO4E comp cover and HKS's .73AR non gated T28 flanged GT30 style turbine housing . I think it came on boost at 2500 rpm and made around 400 ponies at the wheels of a Sentra SE/R . It could have been an old article from the American site Nissan Performance Magazine . By best I mean usable on the street , don't know about the front wheel drive though . O/T but its far far simpler , and cheaper , to fit a GT28RS on the GTiR exhaust manifold for ~ 300 at the wheels - assumes early high port head . Its what I'd do for a road car because larger turbos raise the state of tune enough to make them tiresome to live with .

Also the GTiR's quad throttle inlet system fits the early head . I'd do this because it fits in with the more flow and power for less boost . Factory engineering is hard to beat when they've developed homologation special performance bits .

Cheers A .

Cool Hand Luke Community Regular

Cool Hand Luke

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Hmm... Since the HKS T300 is rated at 450hp im not really sure anymore if it would be worthwhile upgrading to a new one, getting new piping etc made. The T300 started making boost from memory at 3300ish and full boost by around 4000-4200rpm, if possible i could get some input on modifying that.

I've gotten some measurements off it, but are unsure of the trim as i havent pulled the housings off it:

Compressor

a/r .60

Inducer 53mm

Turbine

a/r: .63

Exducer 57mm

Its also due for a service, as whoever owned it before didnt look after it, and has some shaft play, and has damage to the compressor wheel from running no air filter. So i guess my questions are:

If the turbo is rated at 450hp, tuned correctly and everything being normal, should it be making more than 270rwkw?

If it is at the limits of the turbo, when i change the cams/valvetrain apart from the usual power advantages, the rev limit can be raised from the 7300rpm its at now to 9000rpm. Will the current turbo have a boost drop and suffocate the engine at that high rpm?

Would say changing to a bigger exhaust housing fix that?

Cheers - i know this isnt skyline/RB related and might irritate some people, so thanks for the input

Busky2k Veteran

Busky2k

Posted
Posted

Lets see. 450hp = ~330kw flywheel style. So you would estimate around 270-280rwkw would be expected.

By putting a bigger exhaust housing you can probably pick up another 10rwkw but it really depends on whats holding you back. Is the compressor is at max flow or is the turbine choking the engine? Probably the former. Or both.

So, if the turbo is limiting the engine, raising the rev limit will do nothing. On the dyno you'd probably see the power just fall away as the revs rise past the power peak. If the turbo had more steam in her, the power would continue rising.

So yeah, you need a bigger turbo to reach your goals. A turbo rated at least 500hp to get comfortably over 300rwkw.

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