J1mbo

iTrader: (1)

so that means you must drive at full throttle all the time ?

RickyLee53

On the original thread i said it sounds like part throttle surge. I run a 35 on my Evo and get exactly the same under light throttle in higher gears.

Just thought i'd check, as the boost gauge was still wrapped around off the clock

When you say you get no surge, what kind of wastegate duty do you run in the midrange? I.e. I can run above what i've got at the limiter in the mid range with no surge, unless I floor 5th gear, (obviously been my own car i know not to do this)

Chip

iTrader: (3)

A 2.2 would be doing the same at that throttle angle, the throttle is choking the turbo NOT the engine itself, if that makes sense?

Mark Shead

No it means if you want to have full boost on a big turbo use it or drop the boost if you dont want to go as fast.

Mark

Chip

iTrader: (3)

Mapping boost against throttle angle would be the best way IMHO

Right, just going to show granny how to suck on this egg, back in a bit

J1mbo

iTrader: (1)

youve lost me chip

that i understand lol taa

Mark Shead

The wastegate duty is based on what spring you use in it to have the target boost, Mine have no capping to stop surge at any rpm.

Mark

rapidcossie

Happens alot on big turbo cars as you have the foot to the floor to bring the turbo on full boost then have to lift almost insatntly as you realise you dont really need 2 keep foot down as the acelleration is more than enough on half throttle.

CossieRich

iTrader: (1)

Mark,

Can you get a GT30 on my engine without surge do you reckon?

rapidcossie

Surge is when the turbo stalls under full throttle situations.

J1mbo

iTrader: (1)

to get exactly wat boost you want would it not be better to use 2 sets of air injectors
1 set on top of the ex wastegate and 1 underneath ??

pa_sjo

No, the turbo isn't aware of your throttle angle. Surge is surge.


Personally i'd run a more suitable turbo, like a T61 than these 'too efficient' GT turbos that aren't versatile enough for smaller displacement engines!

Mark Shead

I run a Autronic boost valve which is more than good enough, All we needed to do is map it to Daves right foot But he never drove like that in our mapping and he wouldnt have know it can be tweaked.

Mark

rapidcossie

I know the turbo doesnt know what angle your throttle is but you can hardly spec a turbo for an engine on quarter,half or three qurter throttle can you?!

If you start in any gear at low revs and floor the throttle and the pull isnt smooth and the turbo surge's or stalls altogther then its poor turbo choice but on anything other than full throttle its alot more difficult.

pa_sjo

I guess that's what sorts the men out from the boys. You have people who chase peak power and torque figures and throw driveability out the window and then you have those who are capable of providing the entire package.

rapidcossie

You can have the best of both worlds if you try hard enough.

No point having a nice driving car if its 100 bhp down on where it should be.

Rick

A STANDARD RS turbo can be made to surge on part throttle in high gears!

CossieRich

iTrader: (1)

but rs turbos are wank and no one cares about them Rick

Gordon1

a gt3076 is ok up to 550-560 i say as thats what andys makes ???depends on spec tho

J1mbo

iTrader: (1)

ever measure the back pressure at this sorta bhp ?

Rick

I know - thats why i bought a BM

No, point is u stop the air supply, the turbo will stall.

Mark Shead

The most I have seen is 520hp on a internal gate but with a nice exhaust manifold and ext wastegate I am sure 550ish could be had.

Mark

Gordon1

thats what its got lol

Gordon1

thats next on list of jobs to do befor more boost

J1mbo

iTrader: (1)

back pressure gets very high after 7000 and at 8000 it is far too much imo

Turbo Zetec

iTrader: (1)

interesting discussion here boys... keep it up

escossie560

peak power had at just under 7k rev limiter 7.5k

rapidcossie

Harvey did back pressure tests on the GT30's and it was very high.

Turbosystems

iTrader: (5)

your opinion is correct

Martin-Hadland

iTrader: (2)

That is true BUT Lee's car runs a GT30 and uses high boost / revs and has never had a problem, his car is used hard everytime it's used.

escossie560

which model gt 30,internal or external ,what size external its very hard to make sweeping comments with out all the facts

J1mbo

iTrader: (1)

was the backpressure measured on his car martin ?

Turbosystems

iTrader: (5)

i think some people get a little obsessed with back pressure

Martin-Hadland

iTrader: (2)

No but even if it's high it is not effecting EGT's or performance, it will happily rev to over 8k in any gear.

rapidcossie

Not 100% sure what ones it was he tested would have to try and find the threads Mike posted.

Tony why do you think people get carried away over it? I have only ever seen BHP increases from dropping back pressure so I think its right to concentrate on it.

J1mbo

iTrader: (1)

was going very well on saturday so something must be right lol

Benni

Can someone explain what External and Internal means please?

Cheers, Benni.

J1mbo

iTrader: (1)

harvey did the back to back on paul ripleys engine using the gt 30.. < not sure but was external wastegate
did it with the .82 and .63 housing
the graphs

0.82 a/r turbine housing
RPM Bst BP Torque BHP
3000 08 04 199.7 116.9
3500 28 15 360.5 242.7
4000 32 20 386.3 293.1
4500 32 21 404.9 348.7
5000 32 24 394.9 374.7
5500 32 26 394.4 414.7
6000 32 28 395.1 450.7
6500 32 32 389.6 483.7
7000 32 35 376.3 501.5
7500 32 40 341.3 485.4

0.63 a/r turbine housing
RPM Bst BP Torque BHP
3000 13 10 238.8 138.1
3500 32 24 389.4 259.2
4000 32 27 388.3 297.5
4500 32 31 404.1 345.0
5000 32 34 397.0 379.7
5500 32 37 393.0 413.2
6000 32 39 398.7 457.9
6500 32 44 382.7 474.4
7000 32 56 370.8 495.6
7500 32 65 340.3 485.3

J1mbo

iTrader: (1)

benni its the wastegate
weather its built into the exhaust housing or weather it is coming off the manifold ill try find pics