question.

[1dollardog]

What makes the hot air turbo uneffective above a certain boost level? It seems that with the IC'd cars that the more boost the better but in our cars it seems that above a certain boost level that there is no gain in hp. Why exactly.

 

[GARY HARVEY]

It's more to do with the restricted size and design of that intake, not much you can do with that little port
in the back of your manifold.

 

[Boostnitup]

You can overcome it...

Nitrous...

It is a heat saturation point where the fuel/air mixture can no longer be overcome. Some guys have found a way to tune their way into a sweet spot where they go a bit further than the rest of us... dyno time would assist.

Go as large of a turbo as you can make fit... look for one of the rare modified intakes that are floating around out there (V1, or V2), or convert an '86/'87 intake to your application.

You have some options...:biggrin:

 

[charlief1]

The biggest problem is just what boostn stated. You can over come some of this but if you try to squeeze lots of boost through a non intercooled set up then it heats up and can actually detonate inside the intake. Not a pretty thought but it can happen. You can overcome some of this with alky or switching over to E-85 which has a cooling effect on the compressed air.

 

[Boost231]

all turbos have the point of where the start to run over there intended efficiency level. hotair turbos are small thus not having such a great area of efficiency. i was told anything over 25psi on my TA-54 is pressing it over its efficiency level thus every pound of boost over that # is going to heat up the air charge alot. now with the data logging i have been doing at my power level the IAT are already high with meth and 20psi. with no meth the #'s really get up there fast

 

[1dollardog]

So it is really back to the air temp more than anything right? Even though we may use a turbo that is pushing the equivelant air flow as the IC cars, it isn't going to be as effective because the air isn't as cool. Is this right? What can be done to the intake in addition to porting it, to make it better?

 

[charlief1]

So it is really back to the air temp more than anything right? Even though we may use a turbo that is pushing the equivelant air flow as the IC cars, it isn't going to be as effective because the air isn't as cool. Is this right? What can be done to the intake in addition to porting it, to make it better?

That's a pretty good way to put it. It really boils down to air speed and density of said air. You could try to make some sort of pre cooler so the air coming in is cooled before the turbo to increase density but it would have to be compressed so the temp would increase but if you dropped it 30 or 40 degrees below ambeint temp it would help.

 

[1dollardog]

So in our application bigger turbo = more air but more air = hotter air which = higher detonation rate which = catostrophic engine failier. Solution: find a way to cool the intake air. correct? Where are the flow issues with the HA intake?

 

[dr_frankenstein]

air but more air = hotter air

Thats not entirely true. you can have low boost but high volume of air and make better power without pushing the detonation threshold.

The reason "boost Pressure" is even there, is because of the restriction that the engine itself is for the moving air. if you were making 10lbs of boost on a stock un opened engine, then spent time to massively port everything add better valves etc etc....... the boost could drop many lbs - But still make as much or more power as the previous 10lbs. The volume hasnt changed, but the amount of restiction in the air flow path has. And the restriction, is where the excessive amounts of heat come from.

Boost in the non intercooled application can be looked at like electricity. where voltage would represent boost pressure, and Amps to represent volume.

So yes, a bigger turbo is a fantastic upgrade to these cars. anything that can help increase the physical amount of air that is being forced into the engine is your advantage. However, it has been in recent years that HA turbo upgrades have been nearly impossible to find, other than the classic 33 upgrade.

I will have carbon seal backing plate retrofit kits available for all journal bearing turbos within the next few months.... so keep yer eyes open.

 

[Boost231]

stock intake ported should go mid to low 10's IMOP

 

[charlief1]

Aj pretty much summed it up for you. On the intake, they designed it so that the runners were longer to create better torque. If you can find someone that can hydro port the intake you will see an increase in flow and therefor an increase in power. The inlet at the back of the intake has to go down under the top to the front, then into runners going to the head. A long trip in a hot enviroment so it'll heat up more.

 

[1dollardog]

Ok one (one more that is) dumb question. What are all of the "bolts" for in the bottom of the intake? It looks like it will take a 1/2 ratchet to get them out.

 

[dr_frankenstein]

Ok one (one more that is) dumb question. What are all of the "bolts" for in the bottom of the intake? It looks like it will take a 1/2 ratchet to get them out.

you mean the "Core" plugs?

thats where they remove the sand from after casting.

A.j.

 

[tb3]

i would most agree with charlief1.

far as the little port in back of manifold, then a sharp turn,... look at the small hole and even sharper bend in the 86/7 stock intercooler right after the turbo, and the stock intercooler has been in the 10's (i think). i know some have slammed the stock intakes that have been cut open and hogged out, but i know someone local who has had no problems with theirs far as idling and such. what would really be nice is someway to incorporate some sort of power plate like rjc designed for the ic cooleds for ours, but obviously would be very difficult

 

[1dollardog]

If the intake is "hogged out" will that creat a problem of the ports closer to the turbo inlet recieving more airflow than the ones farther away from it? In other words will the cfm's be equal at each port? Will this even matter or be an issue?

 

[tb3]

not sure which ones would get more or less than the others, but no doubt, not going to be equal, course, who knows by the nature of the beast, or shear luck, air distribution might end up being very close. but i doubt it, would need to get it on a flow bench and measure at each port at differant pressures. this is all stuff thats been thought of/tried before i'm sure :smile: i've started the porting/mods on one of my intakes, i may put up some pics when i'm finished

 

[1dollardog]

not sure which ones would get more or less than the others, but no doubt, not going to be equal, course, who knows by the nature of the beast, or shear luck, air distribution might end up being very close. but i doubt it, would need to get it on a flow bench and measure at each port at differant pressures. this is all stuff thats been thought of/tried before i'm sure :smile: i've started the porting/mods on one of my intakes, i may put up some pics when i'm finished

Pics would be great. I have an extra laying around that I may "experiment" with. Like you said I'm sure all possibilities have been tried before by someone. With these cars being around for 25 years I'm sure there isn't anything that hasn't been tried on them at least once.

 

[charlief1]

The bad part about the HA intake is that to properly port it you have to cut it apart or use the hydo port system. If I had access to the hydro system I'd love to do some experimenting with it on the runners under the intake to see how much more flow you can get out of it.

 

[1dollardog]

The bad part about the HA intake is that to properly port it you have to cut it apart or use the hydo port system. If I had access to the hydro system I'd love to do some experimenting with it on the runners under the intake to see how much more flow you can get out of it.

Is there no cutting that can be done from the outside of the intake that would be effective? Looking from the outside into the port (below the injector) it seems like you may be able to cut there and access more air directly from the "lower intake chamber". You wouldn't be "gutting" it exactly but just making air chambers so the air doesn't have to travel all the way around to the top of the intake and back down again to the intake port.

 

[charlief1]

You can do the ports from the outside and it will help flow to some degree but the majority of the intake will be left untouchted. As an alternitive if you can find one of the early SFI FWD intakes it looks like the 86-87 design but mounts backwards. The water outlet will be at the back of the intake but it doesn't have the torque tubes under it so it should flow much better.