Slant Six Forum :: Which turbo?

A T25 doesn't cut it on a stock 2 liter 4G63 Mitsubishi. The boost falls off at high RPM because they can't flow enough air to meet the demand. If you want to run 8 psi boost at 4500 RPM you'll flow about 20 lbs/min through a stock 225. That's a 1.544:1 pressure ratio and 20 lb/min is off the right side of the 60-trim T25 compressor map below 65% efficiency. Things look better at 3000 RPM, but still not great as you're still on the high flow side off the maximum efficiency island. Any mods to the engine to improve volumetric efficiency (flow) and the match looks even worse. A T25 would probably be great on a 225 in an aircraft tug or fork lift, but it's even small for a mild 170.

A Super 60 T3 is about the smallest thing I'd use on a 225. A T04B S-3 looks better.

Play with the various calculators on the Ray Hall Turbocharging web site and you'll have a better idea of what the engine needs. http://www.turbofast.com.au/

Author:	polkat [ Sat Mar 05, 2011 4:31 pm ]
Post subject:	Which turbo?
There have been a lot of turbo'd slants over the years, many represented on this site. Has it been determined what turbo would work best on a basically stock 225? One that would spool up fairly fast and last (to some degree) up to around 5K rpm? I keep reading to use one from a GN 3.8. Good advice? ________ Buell xb12r

Author:	turboram [ Sat Mar 05, 2011 5:42 pm ]
Post subject:
I believe the GN turbo will spool a couple hundred rpms lower than the hx 35 i'm using but the holset is very reliable, they last at least a couple hundred thousand miles. I've had. 2 Trucks with 400,000 mi with the original turbo. But there are many variables to take into account soo what is your planned setup?[/i]

Author:	polkat [ Sat Mar 05, 2011 7:06 pm ]
Post subject:
I just started research on this a little while ago, so I don't have a planned setup as yet. If I go turbo, the car will be a 75% street/25% strip car, so it has to be street reliable. So far my thinking is a stock 225 with a little porting and bigger valves. Haven't given a lot of thought yet to carburter choice (not presently interested in EFI), or ignition. ________ Marijuana vaporizer

Author:	1974duster kev [ Sat Mar 05, 2011 9:02 pm ]
Post subject:
I'm using pte6262 dual ball bearing precision turbo on my duster, my daily driver. Kev

Author:	pishta [ Sun Mar 06, 2011 10:43 am ]
Post subject:
Garrett app recommended a T25..so I got 2! one needs rebuild and waste gate actuator, other is good. Maybe a little small, but im not looking for 5500 RPM performance.

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Author:	Joshie225 [ Sun Mar 06, 2011 11:39 am ]
Post subject:
A T25 doesn't cut it on a stock 2 liter 4G63 Mitsubishi. The boost falls off at high RPM because they can't flow enough air to meet the demand. If you want to run 8 psi boost at 4500 RPM you'll flow about 20 lbs/min through a stock 225. That's a 1.544:1 pressure ratio and 20 lb/min is off the right side of the 60-trim T25 compressor map below 65% efficiency. Things look better at 3000 RPM, but still not great as you're still on the high flow side off the maximum efficiency island. Any mods to the engine to improve volumetric efficiency (flow) and the match looks even worse. A T25 would probably be great on a 225 in an aircraft tug or fork lift, but it's even small for a mild 170. A Super 60 T3 is about the smallest thing I'd use on a 225. A T04B S-3 looks better. Play with the various calculators on the Ray Hall Turbocharging web site and you'll have a better idea of what the engine needs. http://www.turbofast.com.au/

Author:	1974duster kev [ Sun Mar 06, 2011 1:21 pm ]
Post subject:
ya that t25 is gonna run out of breathe the ebay turbo sitting on my desk is a t3/t4 with a 63/ar house but only a 50a/r compressor the maps for this turbo would drop below 75% eff with anything over 8psi so now it's a bookend. Kev

Author:	pishta [ Sun Mar 06, 2011 5:20 pm ]
Post subject:
Quote: A T25 doesn't cut it on a stock 2 liter 4G63 Mitsubishi. The boost falls off at high RPM because they can't flow enough air to meet the demand. If you want to run 8 psi boost at 4500 RPM you'll flow about 20 lbs/min through a stock 225. That's a 1.544:1 pressure ratio and 20 lb/min is off the right side of the 60-trim T25 compressor map below 65% efficiency. Things look better at 3000 RPM, but still not great as you're still on the high flow side off the maximum efficiency island. Any mods to the engine to improve volumetric efficiency (flow) and the match looks even worse. A T25 would probably be great on a 225 in an aircraft tug or fork lift, but it's even small for a mild 170. A Super 60 T3 is about the smallest thing I'd use on a 225. A T04B S-3 looks better. Play with the various calculators on the Ray Hall Turbocharging web site and you'll have a better idea of what the engine needs. http://www.turbofast.com.au/ Thanks Joshua. I actually looked at that site and did the calculations and I got a T25(?) plug these in to the formula and tell me where I am erring: Gas 3800 (cc's) 1 turbocharger Gas no intercooler 8 psi boost (then try 20!) I still get a T25 80??? try it and tell me what you see. Maybe I got 2 because I need 2??? HELP!

Author:	Joshie225 [ Sun Mar 06, 2011 5:39 pm ]
Post subject:
What RPM? 4600 RPM with your other numbers give a GT25 which is NOT a T25. Play with the turbo power calculator and then the compressor flow maps to get a real good idea of what the engine needs. This is a better method as the turbo match calculator appears overestimate the volumetric efficiency for engines like ours.

Author:	Dart270 [ Mon Mar 07, 2011 6:17 am ]
Post subject:
I bet two of those T25s would work well! Lou

Author:	pishta [ Mon Mar 07, 2011 11:30 am ]
Post subject:
They look pretty good in a dual configuration as they are stockish for a 1.8 yoda celica as I have found out. and 2 1.8's = one of our 225's. I saw one in a picture somewhere, dual 3 port headers feeding 2 turbos, dual exhaust..cant remember if the intake plenum was divided to feed 3 and 3 or was it common? Josh, you got any opinion on this? Plumbing would be a challenge but it sure would be unique. I could even get away with 1 actuator moving both waste gates in synch. Or would I run into the same problem, just 2 turbos that are too small? saw this one and asked where the starter went, turns out he moved it with a bellhousing adapter. Then I questioned where the other compressor went!

Author:	1974duster kev [ Mon Mar 07, 2011 1:36 pm ]
Post subject:
Unless your going for a cool factor i think twin turbos aren't exactly worth it for the slant or even in general unless you got a giant 600cube motor and have to have two giant turbos to get the kinda flow required. 2 turbos= more money more things to go wrong more things to fit and fabricate plus from what i've seen the twin turbo supra guys usually go single turbo route as with a few 300zx's i've seen, but who knows i'm just droppin pennies in a can Kev

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