GT42 3X3 VS S400 3X3.2 May 09, 2009 01:39AM
I am currently running a GT42 ball bearing turbo (out of the box) on a 466CI open RPM tractor with a P pump. Our rules allow up to a 3X4 turbo, Will an S400 with a 3" intake and a 3.2 exhaust perform better then the GT42? The S400 will have the larger foot mount. With the GT42 I have always run a lot of exhaust drive pressure (75-80lb) vs. boost (50lb). Different exhaust housing never seemed to make much difference on the ex pressure on the GT42, but did lower the boost a little. Any mods I can do to the GT42 ex housings to lower the ex pressure?

I tried a Holset BHT3B (3"X3.2 I think) at one time and it did not perform as well as the GT42.

Any input would be appreciated, as I don't want to go to the work and expense of mounting this turbo if I am not going to gain anything.

Thanks!
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Re: GT42 3X3 VS S400 3X3.2 May 09, 2009 10:45AM
According to the Borg Warner specs, the S475 compressor will produce 98 lbs of air/min. vs the GT42 compressor @ 96 lbs. per min. so the S 475 appears to be slightly better there. I am only aware of two turbine wheels for the s475 which is a 74 mm exducer with four turbine housing options - the same as the Garrett and the 88mm exducer which has one turbine housing option. There may be more choices however. The s480 has an 88 mm exducer but only one turbine option. It also has a larger compressor.

What housings do you have from your Garrett? I'm looking for a 1.01 T6 flange if the price is right.
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Re: GT42 3X3 VS S400 3X3.2 May 09, 2009 04:16PM
Do most of the classes that run a 3x4 charger, really measure 3x4 (3.00x4.00)? Or do they round to the nearest whole number? (i.e. 3.15x3.62 -HX60; 3.18x3.65 - GT47) are considered a 3x4 turbo.Confused
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Re: GT42 3X3 VS S400 3X3.2 May 10, 2009 02:52AM
Most organizations use a slug to measure the openings to the compressor wheel, like a 3.05 or similar slug to check a charger. There are custom builders of true 3 x 4 chargers out there, but cost a couple of seasons back were in the 4500 to 5000 buck range. The "choke" factor is not so much the 3 intake on the super farms charger, as is the 3 on the exhaust. While a 4.1 charger on a super farm would be greatly superior overall, my opinion is that just opening the exhaust up to 4 inches would make a sizeabe hp increase.
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Re: GT42 3X3 VS S400 3X3.2 May 12, 2009 04:43AM
The S400 turbo I am looking at is a part number 171702. Comp wheel OD is 3.944 and the comp wheel inducer dia. is 2.935. Turbine wheel OD is 3.768 and the turbine wheel exducer OD is 3.467. It comes with a 132 ex housing and I don't know if any other housings are available. While the lbs per minute is only slightly greater, do you think the better flowing exhaust will result in much of a HP increase? Searching the net I have not came up with any factor housing smaller then a 132....are any available. Will this turbo work on a 466CI with the 132 ex housing?

Thanks for the help!
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Re: GT42 3X3 VS S400 3X3.2 May 12, 2009 02:40PM
I ran one for most of a season. I have 470 ci and had to open the 132 housing up some to keep the intake and exhaust pressures closer together. But it really depends on your fuel,cam and timing settings
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Re: GT42 3X3 VS S400 3X3.2 May 13, 2009 09:28AM
I would guess it would work fine on a 466. There was a post on here a while back about someone using an HX60 with a 3.6" turbine wheel on a 466 and said it work fine. There are however always variables and every engine is different. As far as a smaller turbine housing, I am sure a good pump / turbo shop could supply you with something different than the 1.32 for the larger wheeled version if needed. I see there are also different compressor covers available for added performance - so they say.
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