TB42 Turbo Size Guide

[showtime393]

This has prob been covered in other threads but can we get a turbo size comparison thread put in sticky or sumthin?
I'm in the process of seeking my third turbo trying to get the correct size. Started with a cheap chinese turbo, made boost well but was poorly set up and boost was un-controlable. Now I have a garret GT35/40 which has been modified by hypergear (un-sure of specs), made 16psi at 3500rpm. Pulls hard but is to laggy for the bush, find myself hitting things way to fast trying to keep in boost.
Now I'm in the process of researching the right turbo size. Many people have told me that the gt35/40 is way to laggy, but I havn't yet been able to find comparable information. I'm working with Hypergear to try and sort out the correct sizing, he tells me that this size turbo shouldn't be at all laggy on a 4.2 petrol.
So can everyone post real life experiences about what works and what doesn't.
Small housings vs Large housings.
I have a friend who has made over 200rwkw with a high flowed T3. When talking to hypergear he thinks this would severely choke a 4.2 motor.
Can we get as many questions answered about turbo sizing as possible.
I would be under the impression that an XR6 TURBO is a 4.0ltr and a gt35/40 is not laggy and yet a TB42 4.2ltr motor is. PLease explain.
I have 35's with standard ratio's. can this be the reason for all my lagg?

[showtime393]

Thanks for all your help and guideance guys.
Good to see everyone is willing to give some advice
55 views and not one reply

[cooki_monsta]

I use a t3/t4 hybrid, it's an eBay knockoff and works great. Comes on boost at 2000 rpm and holds to about 5000

Oh and don't bitch about replies, it won't get you anywhere

[hiy6o]

Running a GT30/76 1.08a/r seems to work well , (starts making boost from 2200 &15 psi to 5750 rev cut) what did you class as standard gearing? nissan had quite a few ratios. what management system do you have ? try retarding the timing just as it spools makes it happen quiker

[rusty bus]

I think you might find that the 4.0L engine is a lot more efficient than a TB42 when it comes to flow in the intake and port side of things so maybe thats why they spool up quicker?? Also be persistent and do as much research yourself as you can, if you start being a knob because ppl aren't replying as quick as you would like, the ones that know what they are talking about wont reply at all.

[RIZZO]

mate i would personally try different size hotsides first and as old mate said try retarding the timing a little. Cant really compare to a ford 4.0l total different kettle of fish, different manifolds, intakes , heads etc etc. let me know how you go, i have thought about doing the same with turboing 4.8

[turbmav]

The easy way to do it is get the right compressor size (TB42 is gt30ish) with a small turbine housing about AR.69 and a big 50mm external waste gate to control boost.

[RIPNMUD]

having played around with alot of xr6 turbos they are lagy but unlike what alot of people think its not turbo lag its throttle lag due to there being miles to much pipeing ie. a meter of piping from air box to turbo.
so it maybe your cooler set up rather than the turbo

[zookimal]

Really need to know all of the turbo specs to be able to comment for sure. Don't want to send you down the wrong track. What else is in your setup? What's controlling the show? What's the timing map like, particularly below 3500rpm?

What psi is it making at 2500rpm if it's making 16psi by 3500?

sorry, more questions than answers from me

[Northside 4x4]

Sounds like there is something not matched either with the turbo or engine.
(I see this a few times a week from shops that hi-flow turbo's and mismatch them very badly in the process)
Possibly cam timing incorrect or something along those lines.

I have a TB42E with a 35R (1.06 rear housing from memory) in the shop at the moment that we built a few years ago. The only mod we have done to it is fit an external wastegate on the exhaust manifold to keep the boost down.

From memory it was making 12psi by about 2100rpm and about 300hp at the wheels on 33" Mickey MTZ's..

I will dig up some dyno graphs so we can compare the boost curves/afr etc..
I can also pull an ignition timing table out of it for comparison to.