Full boost?
Turbo Mini Forums

Only covered 250 miles so far with my new turbo engine, but already planning to change my T25 hybrid turbo. It starts building boost from 2.5k, but doesnt reach full boost (16psi) until 3.8k. Is this normal? Is rises progressivly ie. 4 psi @ 2.8k, 8psi @ 3.2k, 12 psi @ 3.4 until 16psi. It all happens very quickly, and makes the power delivery very smooth and tractable but I expected slightly less lag and I studden surge of boost.

Where does your boost start to build and peak? and with what turbo?

My current turbo was design for 200bhp+, manily for dragstrip, therefore the spec is

T25 Air cooled Bearing Housing
R5 Machined compressor housing (only housing I could fit with mirage manifold)
T28 Repofiled Compressor Wheel
300XZ Turbine Shaft and wheel
360 Thrust bearing
Etc.

My thoughs now are to try my other newly rebuild R5 T2 to get a comparison.

I like the look of the GT1548 now Ive decided to increase my compression ratio from 8-1 to 8.6-1. My rarget BHP is 150-170bhp @ around 14-16psi. I now mainly want to use the car for road and track days rather than chasing 13 sec quarter mile times a couple of times a year.

Class C 3rd Place Avon 2011 14.18 @101mph

A lot of people here rave about the drivabilty of the gt17, but is the lag really an issue with the car?

Edited by minimole23 on 25th Aug, 2011.

It's not really an issue, I'd just like the turbo to be more efficient and suited to the application. The turbo was the first thing I bought for the project, I wish I'd waited an gone for the gt1752 but I bought a mirage kit and thought I was tied to the T2 range. This is my first turbo mini so I can't compare it to anything expect my mate standard T3, which it's considerable better than.

Edited by alaskanow0 on 25th Aug, 2011.

Class C 3rd Place Avon 2011 14.18 @101mph

I belive a gt17 will fit straight onto a mirage manifold, you just need to construct a downpipe. Do a search though as I think you need to grind a bit out the back of the block above the fuel pump drain and a couple of other tweeks.

A good general rule of thumb is that if you have full boost at 4k, then the turbo will deliver up to 8k. If you have a turbo that will deliver full boost at 3k, then it will be struggling by 6k.

Unless you have a VNT, of course.

Waits to be shot down......

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I plan to rolling road my hybrid and standard t2 to compare graphs at same peak boost. luckily I have free access to a rolling road. I will then be able compare this data to whatever Gt turbo I go for and see what the real difference is. I didn't think the gt17 would clear the block on a standard mirage, so was planning on fabricating my own high flow manifolds which may effect results slightly.

Class C 3rd Place Avon 2011 14.18 @101mph

Thanks Paul, that sounds like the turbo is about right then? At what rpm is the gt17 at full boost (16psi).

Class C 3rd Place Avon 2011 14.18 @101mph

If its a help, my gt17 is on a std mirage, some mods to the studs and a 3mm shave of the block, no bulkhead box on mine either, I cant really give an rpm off the top of me head but to me the 17 seems to build boost very quickly.

On 5th Oct, 2014 Shauna said:
What that's crazy, you go commando hahaha! How heavy is your helmet ?

heres a graph of boost rise ..its in mp but 1000 mp =15psi.



exhaust design (before and after the turbo)
timing
mixture
port size
cam timing
turbine housing

these are just a few of the things that will affect the boost rise . im on a gt17 and its the green line in the graph . as an interesting example , a richer mixture on my car offset the boost rise by 200 rpm.

Edited by robert on 25th Aug, 2011.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

im shit

Edited by oli79 on 25th Aug, 2011.

On 5th Oct, 2014 Shauna said:
What that's crazy, you go commando hahaha! How heavy is your helmet ?

Looking at the graph mines boosts up just like the red, green and blue lines. Panic over.

Class C 3rd Place Avon 2011 14.18 @101mph

What turbo is each off the cars running?

Edited by alaskanow0 on 25th Aug, 2011.

Class C 3rd Place Avon 2011 14.18 @101mph

Robert gt 17, mark clbygtt t3, kean t2 t2clby and at that time arron had a t3 starmag

Drives
-Ford S-max Mk2 Ecoboost
-Rover 100 VVC #2 - track project

Searching is all you need on TurboMinis

So why does the T3 appear to boost earlier than the T2 & GT17? (rich mixture granted). It appears to be 400 revs earlier almost everywhere. Is this a bigger displacement 1380?

Class C 3rd Place Avon 2011 14.18 @101mph

It's a 1380

yep makes a big difference.

Mine was not a standard T2 in that graph, it had a larger compressor wheel.

Kean, was it just the wheel or the housing aswel. I'm thinking of swapping back to just a t25 wheel.

Class C 3rd Place Avon 2011 14.18 @101mph

Wheel and housing mate

I've got what was sold to me as a hybrid T2 but I haven't a scooby whats in it. How would I tell?

I actually think its a mirage one.

If something is worth doing, it's worth doing half of.