Switching from P-trim to Q-trim... what to expect??

[BEATAV8]

What can I expect when I switch from a P trim turbine to a Q trim turbine?

I am expecting lower back pressure..... slower spool.... necesary wastegate changes and modifications.....

Will the engine lean out considerably?
Will the engine tolerate more advance with the lower backpressure?

 

[jasjamz]

What wastegate setup do you have now?

 

[John Wilde]

What can I expect when I switch from a P trim turbine to a Q trim turbine?

I am expecting lower back pressure..... slower spool.... necesary wastegate changes and modifications.....

Will the engine lean out considerably?
Will the engine tolerate more advance with the lower backpressure?

Is everything else staying the same?

 

[BEATAV8]

What wastegate setup do you have now?

stock type. THDP with ported hole. Would switch to a RJC pipe with a monster puck to accomodate the Q trim.

 

[BEATAV8]

Is everything else staying the same?

Would also switch from a cast compressor wheel to a billet wheel (same size 67mm), but treat that separately for sake of this discussion.

 

[Sweet6]

The 6765 P trim has been in the 9s so far. Do you have the P trim maxed out yet? What was your best time with the P Trim?

Ask Jason White about Sean Hayes THS car. I thought it went mid to high 9s around 140ish on a 6765 P trim and a .85 housing. Stock stroke motor and ported stock heads.

 

[BEATAV8]

The 6765 P trim has been in the 9s so far. Do you have the P trim maxed out yet? What was your best time with the P Trim?

Ask Jason White about Sean Hayes THS car. I thought it went mid to high 9s around 140ish on a 6765 P trim and a .85 housing. Stock stroke motor and ported stock heads.

No not maxed out yet, but my P-trim turbine is a bit small compared to the rest of the motor. Stock stroke 109 with ported GN1's and 215/220 cam.

 

[Sweet6]

I read a post about this a year or two ago. I thought Cal chimed in and said the Q trim was only worth about 30HP and it would spool quite a bit slower on the street. Do a search for the thread or we will see if Cal chimes in to confirm.

 

[bison]

There won't be much if any power there till your engine is getting over 75lbs/min. I've done plenty of testing with these wheels. Your combo doesn't really matter unless your using it at 75lbs/min or more. You could have iron heads and smaller cam and be running 28-29psi to hit that flow rate. Your engine should be there around 24-25psi. The old 76p with 67 cast compressor has been 9.80's. The power gain will occur at higher rpm and the advance curve shouldn't change. You're still relying on the piston the push all the crap out of the cylinder on the ex stroke.

 

[BEATAV8]

The power gain will occur at higher rpm and the advance curve shouldn't change. You're still relying on the piston the push all the crap out of the cylinder on the ex stroke.

OK that's along the lines of what I was wondering / thinking about.

No new times / MPH yet, but comparing data to an old 129mph pass, the car is ~4 tenths quicker from 50 to 90mph. Turbo is holding 27psi OK but at 28 psi it seems to fall off a bit around 5500RPM and up.

 

[Sweet6]

Based on other cars with this turbo I would think you would be trapping around 140 MPH at that boost level. You have little more cam and heads than the car I am refering to as well. 206 cam ported stock heads 28lbs was 9.80ish at 138MPH from what I remember him telling me.

Probably best to run it at the track to see where you are at. Buick club is going to Byron on Sunday!! lol

 

[BEATAV8]

Haha it's not quite that fast but it's well into the 130's I'm sure. Still messing with spark plugs and such, plus it's gonna be a hot one this weekend and I'm hoping for some cool air, so I don't think I'l have this car at the track but maybe, we'll see. Always got the blue one as a backup.

 

[bison]

Based on other cars with this turbo I would think you would be trapping around 140 MPH at that boost level. You have little more cam and heads than the car I am refering to as well. 206 cam ported stock heads 28lbs was 9.80ish at 138MPH from what I remember him telling me.

Probably best to run it at the track to see where you are at. Buick club is going to Byron on Sunday!! lol

That would be a very strong running engine to run 138mph with those "minimal" parts by comparison to others here for sure. John Crawford hauled the mail with an old 6776 and off the shelf hyd roller and that was at least 3 years ago.

 

[bison]

OK that's along the lines of what I was wondering / thinking about.

No new times / MPH yet, but comparing data to an old 129mph pass, the car is ~4 tenths quicker from 50 to 90mph. Turbo is holding 27psi OK but at 28 psi it seems to fall off a bit around 5500RPM and up.

The t04z compressor wont start to fall off till over 75lbs/min. Its a bear between 65 and 75lbs/min@2.5-2.8:1 pressure ratio which is why it was used so successfully on these engines. 134-135mph in ok air. In good air running it hard it will go over 138mph

 

[Sweet6]

That would be a very strong running engine to run 138mph with those "minimal" parts by comparison to others here for sure. John Crawford hauled the mail with an old 6776 and off the shelf hyd roller and that was at least 3 years ago.

I was told this by Jason White. Don Cruz built the engine. Ported stock heads and 206 roller were the basics of it. Maybe jason will chime in. He tuned the car and built the trans.

 

[bison]

I was told this by Jason White. Don Cruz built the engine. Ported stock heads and 206 roller were the basics of it. Maybe jason will chime in. He tuned the car and built the trans.

I dont doubt any of it.

 

[bison]

stock, 76 P, GTQ

 

[bison]

to4z compressor aka T67

 

[BEATAV8]

thanks for posting the compressor map

 

[Sweet6]

Thanks for the pics of the wheels.