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Discussion Starter #1 (Edited)
For experienced T-78 autos owners: I’m in the final stages of assembling a T-78 kit with Eagle rods and freshly built bottom-end. I have a T-78 with a BL 4K stall combination that some people are very happy with for the street. I've heard lag is negligible and 10's is doable. From expereince how much truth are in those statements? I have 750 Siemens injectors, port & polished head with oversized valves, HKS 264's, 8K Gforce, C-chip, stock tranny.

Thanks, Mitch
 

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Mid-life Realization!
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Your stock tranny isn't going to like you much if try to utilize the capabilities of your other mods;)
 

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Discussion Starter #3
Yep I know, BL is in the near future. I figure the stock tranny has only 40K on it as long so I don't do 6K hole shots with slicks it should last a few months.
 

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I 4000 stall isnt hight enough you will need to get a 4500 in order to do good launches. without NOS.
 

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blackbird said:
I 4000 stall isnt hight enough you will need to get a 4500 in order to do good launches. without NOS.
Please explain why. What would be the perfect match with my PTE67 (P)?

TIA. :)
 

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blackbird said:
I 4000 stall isnt hight enough you will need to get a 4500 in order to do good launches. without NOS.
WHY? the T-78 is only a 66mm turbo or thereabouts. 4K stall is Plenty for that turbo.
 

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banton said:
The 4500 stall would help for launching, but would suck for driving around town IMO.
Yeah i can see that. My 4K wasnt too bad. Car would start moving about 2200 or so.
4500 might be excessive.
 

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On the T-78 the I built you couldnt build up enough boost at the line with a 4000. your right a 4500 on the street would suck. thats why I went with a different turbo. The T-78 is to laggy and the new turbos are so much better. A t66 with a GT wheel would be much better and a 4000 would work fine with it. the Problem with the T-78 is that the AR is to large and its hard to change out to a smaller one.
 

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I still fail to see why everyone thinks the T78 is too laggy. I wish there was a fair comparison of these newer turbos against a T78 to see the difference (not that crap that was posted on the PHR website). My T78 is spooling hard (20 psi) by ~4100 in 4th gear. I've got datalogs showing this. Until I see a fair comparison, all these statements about T78 being too laggy is bogus. If everyone considers 20 psi by 4100 rpm is laggy, then I'll stop posting these responses (seems like a weekly thing now, everyones dogging the T78). I've heard of cars running T78 with lots of lag, but I suspect the health of the engine or state of tune is questionable. With a properly tuned engine, T78 are very capable IMHO.
 

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On the freeway the T-78 is great but in 1st gear the lag is to much for an auto to get any good 60ft times.. the T-78 kit is a great kit I just wish that is was easier to find a smaller AR housing.
 

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Here is a dyno comparison between the old T-78 kit and my new sc61 GT turbo. The only difference in that the T-78 kit was running 24psi on race gas and the SC61 was running 20psi on Pump gas.
Both dyno's were done in 3rd gear at 80mph so the auto wouldn’t down shift. As you can see the SC61 was already going when we hit the gas no lag. The SC61 didn’t put out the same power but it does show the difference in lag. Its hard to show a good comparison. I need to do a run in 1st gear only.

The Blue Line needs to be shifted over to the left its off, boost came up at 5200 not 5800 rpm but it still gives you the idea.

T-78 is in Blue
SC61GT in Red ....58 AR housing

 

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BlackBird,
Looks like the blue curve is set to the left by 1k
rpm not 600 rpm if both runs were taken to
6800 rpm. BTW, how can both runs begin at 80
mph in drive on the same car and differ in rpm
by 600-1000 rpm? (after shifting curve over).
Do you have any runs that that you could post
that would be more "apples to apples" so we
could get a better idea? Better yet, does anyone
have those AEM logs HAU asked for?
Thanks
Wayne
 

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How big is an SC61GT? Is it comparable to a T78 in size and power? What would be perfect would be a comparison between a 67GTQ or some DBB turbo similar in size and power output to a T78, now that would be interesting. T78 is definately old technology, but I don't think it deserves to be labeled as too laggy. I wanna see if all the hype about these newer, quicker spooling and $$$ turbos is warranted.
 

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The SC61 is a small turbo. Its the AR on the exhaust side of the T-78 turbo is the problem. The T-78 has a .90 or so AR. Great for top power. The SC61 has a .58. Good low power. Its the Exhaust AR size thats important here so a .58 to a .70 AR is good for the street. IMO I sold my T-78 Kit because it way too hard to find a different AR Housing. If you can find a .70AR for the T-78 that would be great. Im going to get a .70 AR for my SC61 and drag race with it, and use the .58 for the street.
 

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Talk to John Minert.... he was running a T78 with supporting mods with either a 3800 or 4200 stall convert IIRC. That seemed to work out great for him.

As for the lag of the T78... everybody over exagerates it. :)
 

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Im the one who built johns car with him. we got the T-78 Kits at the same time. Check out my web Site With johns new grey supra and my black one.http://www.utahracing.com/page2.html

Here is a link to johns old T-78 Blue Supra http://www.utahracing.com/supras/john/bluemk4auto.html


Craig King said:
Talk to John Minert.... he was running a T78 with supporting mods with either a 3800 or 4200 stall convert IIRC. That seemed to work out great for him.

As for the lag of the T78... everybody over exagerates it. :)
 
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