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October 16, 2026, 11:58:04 PM

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[XMAN]

What would happen to a 250 crossflow in the way of performance/and or failure with a T3 .63 exhaust housing and a a/r .60 front cover.  Mild cam , decent exhaust and programable fuel injection.   Would this turbo be to restricive for a mild application with a rev limit of 5000 rpm and manual trans.
Cheers

[TE-Jano]

A guy I work with did a similar thing on a Falcon. Small turbo off a jap diesel on the 250 with stock cam, log manifold. Not sure of the turbo specs, it had unbelievable bottom end torque and power,spooled instantly,  would waste most of his mates 302 & 351 off the line, but when he got to 4000rpm it was like the engine hit a wall. It would not rev any higher. He ran stock pistons and eventually broke one.

 Just need to work out how much air the engine will flow with the mild cam and compare to the flow specs of the turbo.
I could probably punch out some guideline figures on flows if you need a hand with it.

Hope this helps ya.

[TE-Jano]

Curiosity got the better of me and ran some numbers anyway. The T3 you mentioned sounds like a T3/4. Do you know what Trim the wheels are?

Naturally aspirated 250 xflow @ 5000 would flow around 275cfm with VE @ 75% at atmospheric pressure (14 psi). Add 14 psi boost from your turbo, this would equate to around 550cfm @ 5000rpm. The T3/4 with "70 trim" wheels would would handle it for a mild setup, but would be approaching its limit. This is just rough ball park stuff but you could expect somewhere in the region approaching 300HP from the setup you mentioned. Better off going to T04E if you don't already have the turbo, it would do the job much easier. Im sure other guys here would most likely agree. Just my thoughts anyway.

Hope this helps.

[XMAN]

Cheers Jano , Good info thanks, with the t04E what size are these? Ive got two cheep turbos the other has a 1.15 exhaust and .60 on the front . Will the 1.15 housing be to slow to get on boost? As my aim is to have lotts of low down power and keep strong all the way to 5000rpm.

[TE-Jano]

Gday XMAN,

T04E has .84 a/r on the hot side & .50 a/r on the compressor side. The one you have with 1.15 on the hot and .60 compressor, these usually used on a 13B rotary and are good for 600+ HP, not real good for your application though. You could use it if you ran an auto and a hi stall convertor but not to good with the 5 speed for bottom end.

There is nothing wrong with using the T3/4 you mentioned in your first post, it will spool early and still be going at 5000rpm, you'll just be working the little thing harder (more boost to achieve the same power) than a T04E. Put it this way a friend of mine has a single T3/4 on 308 in a 1 tonner, it shreds tyres like theres no tomorrow,  and its a cheep one as you put it (made in china). You just need to know which cheep ones to buy, I've used chinese made before and have not had any problems. Also look at the Skyline and crummiedore guys, a lot of them are using T3/4 or GT35 and making good streetable power from 3lt engines. The 250 will just spool it quicker.

From the sound of what you want to do, I'd go the T3/4 since you already have it.

Hope this helps.

[Vince]

Hi guys,
I'm in the middle of putting together a 250 xflow for my TD. I got myself a Turbo for it and wondered if anyone could tell me what I have and if it will do the job. The 250 is an injected alloy head from an XF and I'll be useing a mild cam and ported head etc.
I got the turbo off an RB 30 VL who went up to a HKS T51R. It's fully polished so I don't know if there was any markings on the main body other than 'J84' and '8' that are just visable.
It has plate on it that says 'T3' and 'Super T7' Also on the back of the is 'K27.015'
The exhaust wheel is 65mm diameter and compressor wheel is 62mm.
Any help would be appreciated
Thanks

[TE-Jano]

Gday Vince,
J84 is usually found on T04e housings and the K27.015 is a KKK marking. At a guess it is probably a T04 Vband or T70, probably either chinese made copy or Masterpower or Precision, similar to a Garrett T61. Does it have single or double entry into the exhaust housing?
By the sound of your wheel measurements it probably has a .70 a/r compressor and .84 a/r turbine, good for around 500HP.
 Does it have coolant lines as well as oil lines from the centre cartridge? If not its probably a copy.
These are quite a common upgrade for RB25 and RB30 guys. Punch the numbers into google theres heaps of stuff on them on the net.

Hope this helps, Chris.

[Vince]

Thanks Chris.
It has a double entry into the exhaust housing and no coolant lines. Sounds like it will do what I want with this engine, hopefully it holds together as it seems to be a copy of some sort. I'm looking at running around 350hp maybe 12-14psi boost.
Thanks again

[TE-Jano]

No worries,

At 350hp she'll still be a street weapon, may not even need to run that much boost to achieve 350hp.