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Old 02-04-2009, 07:57 PM   #1
lcvette
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Default 78GTS Vs. PT88 Turbo dyno overlay comparison

Hey guys some have requested this so I wanted to sho a bit of the difference in lag and performance. obviously when you look at the Time chart you notice how much laggier on the dyno (which doesn't load the same as the street) the PT88mm was in comparing to when the throttle was hit to when it began making power. but also keep in mind that that short blast propelled the dyno roller from 65-125mph in less then 4 seconds.. that my friends feels unreal on the street!

I know I really wanted to see a comparison on this since so many people get caught trying to decide between the two turbos I tried out, so at my expense here is an apples to apples comparison of two turbos on the same exact motor with nothing else changed. note the PT88 on the same exact boost settings made 24psi and the 78GTS made only 22psi. my guess is the lowered back pressure of the larger turbine wheel afforded some new flow and didn't forced the wastegate open as it appeared to be doing on the 78GTS due to elevated back pressure.

Here you go I put them in comparison on speed, engine speed, and time so you can see the different spool characterists in more of a dimensional comparison.

Enjoy!


Click the image to open in full size.


Click the image to open in full size.


Click the image to open in full size.

Last edited by lcvette; 02-04-2009 at 08:05 PM.
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Old 02-05-2009, 02:17 PM   #2
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Those are some very interesting numbers.

The peak torque seems to have similar TQ/PSI(+atm) numbers. Even though peak torque seems to be at a higher rpm on the PT88 curve.

The HP/PSI numbers are well different giving the PT88 about a 70hp difference if you do a quick calculation to match the HP numbers at 24psi. That GTS turbine on the 76 seems to start cutting power around the 5k mark.

I wonder what these two curves would look like if you were only running 15psi. My guess is the smaller airflow would not let the 76 hit its max and the peak numbers for both turbos would be closer to the same.

I really like the graph of power vs time. This gives you some real data as to how much extra spool time it takes. And from looking at the dyno graph you can see that the bigger turbo takes about 500rpm more to spool up.

I can't wait to see what you do with your next setup and a new cam. This thing should have no issues hitting the 1000rwhp mark.
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Old 02-05-2009, 08:43 PM   #3
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246/239 113lsa solid roller and some knarly pushrods. 260lbs on the seat 400 over the nose + victor Jr single plane and that 355 will **** right up to 7600rpm Pt88 willl really shine there.

Chris,
the ford powerstrokes come with a factory TIP sensor. It's like $120 from the dealer.
Does your pCM have a spare A/d channel?
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Old 02-06-2009, 09:48 AM   #4
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Quote:
Originally Posted by Baldturbofreak View Post
Chris,
the ford powerstrokes come with a factory TIP sensor. It's like $120 from the dealer.
Does your pCM have a spare A/d channel?
Mopar has them for sale too for about the same price. But what is it good for? This is the Throttle Inlet Pressure, right?. Isn't that just the pressure in the intake pipe before the throttle body?
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Old 02-06-2009, 01:39 PM   #5
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246/239 113lsa solid roller and some knarly pushrods. 260lbs on the seat 400 over the nose + victor Jr single plane and that 355 will **** right up to 7600rpm Pt88 willl really shine there.

How often do you think the rocker will need to be adjusted if one were to go this route with a solid?
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Old 02-07-2009, 04:23 PM   #6
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Turbine inlet pressure,Brian.
It would be sweet to know what the Turbine inlet pressure/Intake manifold pressure ratio was. Tells the whole story with your turbo setup, cam timing etc.

Bill,
With a nice 7/16 stud & girdle, good rockers, maybe once every season. Unless he DD's it and takes it to the stutterbox all the time. Maybe twice.
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Old 02-07-2009, 08:50 PM   #7
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Quote:
Originally Posted by bill mcdonald View Post
How often do you think the rocker will need to be adjusted if one were to go this route with a solid?
Speaking as someone who runs a large SR cam, I will pass along my experience. When initially installed, I checked it after a few hundred miles, then after a couple of months, then after six months. That first adjustment and the one at ~8 months, there were some slight adjustments, but each time I check it lately, everything is right on. Unless there were noise, I would have no reason to check the lash.

With shaft rockers, good valvetrain, and basic common sense with regard to driving, there should be no issue with the "tight lash" SR cams.
Aaron
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Old 02-08-2009, 09:35 PM   #8
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I will be pulling everything down this week in the evenings and getting it boxed up and some pictures taken of everything to send off to the new owner.

then the motor will be coming out to be gone through and get a new cam and the single plane intake manifold and some additional underhood weight reduction and room making, I have decided to turn this acr into more of a track/street car then a street track car.

so hopefully in the very near future the new setup will be complete and I will be getting some new numbers for you guys and some track seat time to start dialing it in and honing my big power driving skills.

tracking a car with power like this is a very different task then a 400rwhp car, it requires a great deal of finesse and alot of *****....lol

I will of course keep the forum updated with pictures of the new build and hopefully figure a way to keep the IRS alive.

Aaron,

any siggestions on how your monster is holding together? I need some direction and am not quite ready to make the swap to a solid axle just yet for some personal goals I am setting for myself for the rest of 2009 and 2010.

Thanks!

Chris
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Old 02-10-2009, 01:43 PM   #9
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THere is a new Gt5533 with a 94mm inlet (vs the other 91mm), and a new Gt5541R (106mm inlet)
Availible in .90 hotside...
Just in case your thinking about building a different setp again.
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Old 02-11-2009, 10:28 AM   #10
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Aboput the spool-times.

I saw something interesting on a tractor pulling engine. They had built a restrictor plate with only a small hole, like tiny ...
Before start they revved the engine with the restrictor and that maked the huge turbo spool like crazy. Then they removed the restrictor when they started the pull.
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Old 02-11-2009, 02:51 PM   #11
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Aboput the spool-times.

I saw something interesting on a tractor pulling engine. They had built a restrictor plate with only a small hole, like tiny ...
Before start they revved the engine with the restrictor and that maked the huge turbo spool like crazy. Then they removed the restrictor when they started the pull.
where is the plate mounted?
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Old 02-12-2009, 01:20 PM   #12
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Quote:
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where is the plate mounted?
Pre-compressor. The idea is the compressor "freewheels" in a partial vacuum until the shaft speed is up. then dump the air in.

The used to do the same thing in F1 cars. 2 throttles.
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Old 02-20-2009, 12:35 PM   #13
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Oh snap! Did every one know that BW has a 122mm (WOW!!!) inlet turbo??? It's called the S15122, and can flow over 250(!!!!)lbs/min.
Placed in the nose of your car, I believe it will consume(gulp it right up) about 1/3 of your frontal area.
Unreal.
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Old 02-20-2009, 12:35 PM
 
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