crashly

cool,

thanks for reply...
what cam you using, and what rpm range the engine working in?

thanks
ash

Andy02Z

iTrader: (1)

What do you mean by it stops pulling? Are you saying its doesnt rev any higher? It sounds like it could be fuel delivery if it reved higher with the smaller turbos.(larger turbos producing more power and require more fuel at lower rpms??)

Have you tried running to motor to redline with a regular set of headers and no turbos? The motor shouldnt need the turbos to rev.

Have you measered back pressure? I think if it had to do with too large an a/r it would rev fine just make boost late/slow. It would make more sense to me that too small an a/r would stop the motor from reving higher do to back pressure getting too high. Although I doubt this is the case here.

I am no expert just trying to help. Who is dynoing the motor?

Andy

Andy02Z

iTrader: (1)

but your running alky and he is running gas. From what I understand alky needs larger turbine sides compared to gas.

ALLBOTTLE

iTrader: (13)

My setup was specd with .96ar housings for use with c16 and a 8500rpm operational limit.

looking at about 2 weeks to see if it'll work,lol

crashly

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you talking about this post??
hellbents,
thanks for reply.
already have the .81 's , they sppol to 4000rpm on flat stall, but engine will not pull up any higher, even if i wind up manual bosst valve. If i put the twin 61mm back on, it goes to 5700 rpm...

i think the 76mm turbo's arenot in there sweet spot...
just trying to gte ideas what exhaust a/r's tp put on..

how do you think .68 a/rs would go?
thanks

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the engine went 7.2 @ 191 with twin 61mm turbo's ( gtk 550's, great response, easy power transistion , no big power spikes...)
put the twin 76mm turbos on with same torque converter, and re calibrated fuel system, the engine ONLY got to 4000 ish rpm... no matter what i changed the reg to... ( 20, 30 , 40 psi it only got to 4000 ish rpm and 10-11 psi )

i put it down to the .81 a/r with s trim wheel
61mm turbos had stg 5 wheel with .81 a/r
fair bit of difference

either the converter is too tight for the twin 76mm
OR
there isnot enought exhaust gas to spinn the s trim wheel in the .81 a/r housing...
i bought a set of .68 a/r housings ,to suit the S trim exhaustb wheel, and a looser converter...
have not tried either, have been too busy with my business to play with "toys"....

i think the .68 a/r housings will bring the full spool up down 500 rpm, from the .81 a/r's , and the original torque converter will work...
last couple of passes , there is only 3-4 % t/c slip from the data logger
the engine was doing 6800 ish for the 191 mph, it only has to do 7000 rpm and that equals 200 mph,
and 7500 rpm is 214 mph
that is ok, as the 3.7 : 1 diff ratio will "calm " the car down on the start line, and the 34.5 -17-16 tyres , and only need 205- 208 mph to run with the screw blower boys to be competivtive.

this twin t76 ( twin gtk 1000 turbo's ) engine has not been dynoed yet, last engine was dynoed ( 57 mm turbo's, turbonetics to4 super E's with t3 stg 3 turbine hot side.)... thats where the hp figures are based.
using the " morso slide" to work out hp and data from drag time slip with 61mm turbo's.
on a flat stall, no msd 2 step rpm chip installed...
with twin 57mm turbos, this t/c went 4600 rpm with 16 psi , or 850 hp,( dyno hp and boost settings), 5600 rpm with 24 psi or 1016 hp...

with twin 61mm turbos, the t/c went 5800 rpm with 30 psi, or showed 1000 + hp at the wheels via drag time slip and morso slide rule....( 7.2 @ 191 with 1900 lbs race ready)

with the twin 76mm turbos , it will not pull past 4000 ish rpm with what ever boost i adjust the reg to....
i think the converter it too tight , or not enough gas speed to enable the turbo's to start making any real power...

cheers
ash

Andy02Z

iTrader: (1)

Ok, I misunderstood your original post. I thought you were saying that the engine would not rev past 4000 rpms at all.
The a/r change makes sense to me now.

crashly

any more input...
what will the ceiling for .68 a/r housings with s trim wheels
will i get to 7500m rpm ??

ta

ayousef

Wow speaking about wht you know

onfire

iTrader: (17)

How did the tests go crashly?

crashly

not used the 76mm again..
they are sold
getting a pair of 78mm , to be put on the shelf for later
i did not want to cut open the 10 converter, as its middle of the season..

i did find tho , the msd crank trigger wheel had a bad magnet in # 4 AND #7 positions.
the spark plugs showed LESS ignition timing on the earth strap.
i think this hindered the engines ability to make enough power to pull up on the converter.

I am waiting for the 400 cube rotating assembly back from eng balancers, 78mm turbo's will go on that engine

Ended up getting another set of 66mm for the 358 cube engine.
Hmmmm nice little package that is.
The converter allows the turbo's to spin up , and now @ 27 psi, it pulls the converter to 6050 rpm flat stall.
Had to put a bit more fuel in now, flowed a new system to 4.56 gal/min.

will get results later

cheers
ash