Yes, we are in agreement there. And as far as what the LT-1 bottom end can handle, well, I'm a little concerned also, but I guess we are just going to find out...

I have more than one, so if something happens I have options. Guys are getting away with it with their LS engines, so I figure it'll last a while, anyway.

This engine looks to have at least a 100,000 miles on it, and should be loosened up good already. When I tear it down to change the cam, I'll check all the clearances and put extra gap in the rings, among other things.

 

I appreciate you taking the time to work that up. I don't know what rpm your dots represent though.

And what did you instruct me to do before? Other than to run each side sequentially, which I was already planning to do anyway?

 

I didn't say I couldn't get another one... Where did you get that idea? It just wasn't part of my plan, so I hadn't even thought about it. I know where I can get one right now for $40.

Thing is, they are even bigger than the TPs.

 

Orr, I've spent hours looking on the web today, and there are apparently no GTP-38 compressor maps to be had. But from what I can determine, the wheel sizes are the same as the older TP-38, only the A/R on both sides has been tweaked some. I think I read somewhere that the hot side A/R is .85, and the blower says 1.0 A/R on the housing.

This is a little confusing to me (same size wheels), because the turbo itself looks physically larger, plus the pressure piping on the engine is literally twice the diameter,

Here is a photo of the GTP for reference. If you've never seen one, it is twice the size of the GN turbo. and that valve at the bottom can shut off the exhaust exit completely.

GTP-38


From what I have read here and there, it would seem that the TP-38 may be roughly comparable to the GT-35. Here is a map, and a screenshot with some helpful information:

TP-38 Map


Does any of this help make the picture any clearer?

 

On that map i am getting different Pressure numbers than crossfire did. No way you’ll see pressure ratios much above 2 imo to get that power number. But he said stock lt1 so that could be the difference

800 flywheel on a cammed lt1 should happen by 15 psi or pr of 2-2.1. Thats 80 lbs a min. Give or take, on e85 it helps make more power than pump gas.

a single tp38 would be riding all over the choke side of the curve. Even at low boost numbers. Simply isnt enough compressor to feed the demand.

but the turbine side is good for some power on that car, it just be better if it was matched to a 70-76 mm compressor. This would be like the old Q trim optioned T70-T76 master powers. They were fine for 500-600 whp ish. Turbonetics tc series same thing, good small single turbos for a smaller motor and medium hp

1.15 t4 with a 70mm turbine is abit large imo for what spool you want as you already know. But small compressor wheel it wouldnt have problems coming up, just doesnt have the airflow. If that quick spool valve works well then it would be needed in a midmount situation. Front mount it would work good imo. I was able to spool a t70 pretty quick on my 305. .96 ar 64-74 wheel. An lt1 shouldnt have issues. But you just need more compressor....hence the second turbo...

it comes down to can you properly split exhaust duty to control both turbines as to not overload one or the other and get the compressors making boost at similar times as to have flow in one direction to the motor.
having the small turbo making 5 lbs at 2000 rpm while the other is not making boost yet cuz it aint spooled is what im not sure how to do. Valving/check valving but thats alot of stuff to add that idk how you control with software and you’d need them in 2-2.5” sizes.

twin tp38 would be perfect if a front mount setup. I just think it wont spool as good for you in a mid mount setup. Atleast not for a street car thats kicking it from a roll with a tight converter. I wouldnt mind it but it sounds like you want blower response

 

Thanks, I'm sure I missed the full impact of what you were saying when you the were comparing all the different turbos that I am not familiar with. But I think I got the gist of it, and I'm satisfied that some of the other old timers here did know exactly what you meant.

So, as I see it... what you are saying is, that either my original idea (GN + GTP), or the two TPs, should work reasonably well in my situation... if, I can set up an adequate system of stage valving. And I'm not concerned about one of them overriding the other. I know how to handle that.

I've never done it with turbos before, but I have done similar things with industrial piping and ducting. The theory is the same, and I would not expect to experience any issues.

Now on the other hand... If I used the TPs, I would have to either run them as twins and shut off one side of each turbine at low rpms. Or combine the exhaust, and stage them sequentially. It would be very complicated, but I could actually combine the two methods, and achieve very fine control.

I just keep thinking that the two TPs, are too much turbo for my application. But we think a lot alike, I think at this point you have a good grasp on what I'm trying to do, and I trust your judgement. Just put the valving difficulties out of your mind, and tell me what you think is the best overall choice. I'll run with it from here.

Really appreciate the help, BTW.

 

honestly like the idea of this. Basically quick spool valves which i want to explore on my own setup to be honest. Lol. Ultimately if you can figure out how to be sequential with tp38’s using possibly both methods of control it will do what you want. One will spool pretty fast. Esp half turbine blocked off temporarily. Its up to you.

 

Okay, I suppose I'll just use the matched pair then.

I still feel like the two are a little more than what I need. But I can always put a 383 kit in the engine, and bring the CFM (and "tire melting torque") up that way if necessary.

This'll make Crossfire happy, anyway...

 

Do what you want, either way will be interesting lol. The tp’s will give you more room to grow because ultimately you will have to go forged internals and you will want to turn the boost up

happens to everyone who has a turbo setup lol. And a true 800 hp will be more efficient with twin 60’s

 

Orr, I honestly think I'll be happy with the 800hp. I'm going on 70 years, and my testosterone level has dropped considerably in the last 15 or so.

All I'm looking for with this build, is a nice budget aircondioned sleeper/driver that will perform respectably in an occasional impromptu roll race. It's not even an SS, just a little black coupe.

I have a built Procharged Z06 that makes a little over 700 at the tire, and I could easily gain another 200hp just by changing a pulley. But it's already fast enough for me... Frankly I wish I had some way of conveniently turning it down instead, for ordinary driving. I hate having to be so responsible with my right foot.

However, if this works ​​​​out the way I planned, then later on I want to build the 540 Grand National that I mentioned earlier in the thread. Then I will be looking to make at least 1,200hp, but that will be a whole different animal...

I'm sure I will be calling on you for more assistance as this current project progresses. I sincerely appreciate your help and opinion.