Sucking air through a straw

[UncleDave]

In the middle of doing a hot air 4.1 build and started thinking about induction. HA setups draw air through the throttle body - like sucking through a straw. If this is an area of restriction on the 3.8, it would seem to be exacerbated on a 4.1. Just experiencing the difference a big mouth cold air kit made on my '84 tells me anything that increases inlet flow is going to help.

So, in conjunction with a big CAI, large bore MAF, and significantly larger turbo, has anyone tried adapting a larger throttle body from, say, an LSx V8? You'd have to fabricate a TB-to-turbo adapter, throttle and kick down cable bracket(s), vacuum block, etc... But it sure sounds like a fun Frankenstein project to try.

Now, those who know me well enough realize that once I get an idea in my head, things can start moving quickly. So if this is a bad idea, someone please talk sense into me before I open the wallet...

 

[Boost231]

I have been trying to find someone to make me one. Can't really find anyone on the west coast that can. If you do this please please contact me. I need one and am willing to send money. I have a idea for the size I want / need. I have been looking at fast throttle body for lsx and fords. Problem I see like you posted is getting the linkage to fit using the tv cable and also the tps iac location and size.

 

[novaderrik]

how fast are guys going with the stock throttle body? unless your 4.1 is going to push your car into the 9's or something, it would probably be a waste of time to go bigger.
i also think an LS throttle body would probably be a waste of time since the inlet bore on the turbo would be so much smaller than the bore of the throttle body.

 

[UncleDave]

That would sort of make sense on a stock turbo or even a TA33C which have small inlets, but I'm talking about much larger turbos.

My thinking is two-fold. First is matching the size of the TB outlet to the turbo inlet and port matching for smooth flow. Second is the cfm of the TB under vacuum. This is important on a draw-through since the TB is not pressurized; on the IC cars the TB is under pressure, diameter is less of a concern at moderate power levels.

Take your '87, bolt on your LS1 MAF/Translator and 4" cold air kit and go have fun. What if you moved your little stock '87 throttle body from after the IC to in front of the turbo, what that will do to your air flow and thus HP? I bet the car would act asthmatic in comparison. Now you've just created the same situation as the hot air cars. It seems reasonable that you want a TB that, rated under naturally aspirated conditions, matches the cfm of the turbo. Even with a TA33C, you're trying to feed a 700 cfm turbo through a 500 cfm throttle body. Porting will help to a point, but when adapting an even larger turbo it will be a restriction.

 

[fyrlt67]

You can have your stock TB reworked, this is who did mine
84
He did a great job and the turn around was fast

 

[bearnone]

tr customs has a nice 4inch big mouth setup i have it on my 85

 

[Jerryl]

In the middle of doing a hot air 4.1 build and started thinking about induction. HA setups draw air through the throttle body - like sucking through a straw. If this is an area of restriction on the 3.8, it would seem to be exacerbated on a 4.1. Just experiencing the difference a big mouth cold air kit made on my '84 tells me anything that increases inlet flow is going to help.

So, in conjunction with a big CAI, large bore MAF, and significantly larger turbo, has anyone tried adapting a larger throttle body from, say, an LSx V8? You'd have to fabricate a TB-to-turbo adapter, throttle and kick down cable bracket(s), vacuum block, etc... But it sure sounds like a fun Frankenstein project to try.

Now, those who know me well enough realize that once I get an idea in my head, things can start moving quickly. So if this is a bad idea, someone please talk sense into me before I open the wallet...

Dave,
I like your enthusiasm.
The question I have is; ”What are your performance goals?”

It is my humble opinion that when you are at a point to make a custom TB, in your search for HP, in the stock configuration, your efforts would be better spend rethinking the stock HA set-up.

Edit:
Your analogy of “sucking air through a straw” is correct.
The question is; How much air are you sucking and what is the size of the straw?

 

[LOT]

First is matching the size of the TB outlet to the turbo inlet and port matching for smooth flow.

I once had an 85 throttle body bored to match the turbo (66 MM I believe) Went through to the outside--did some welding and rebored. You are right in that they should be the EXACT same size and MATCH.

 

[boostmaster]

Throttle Body

I have a 63MM compressor wheel on my turbo with an aftermarket throttle body from Steve Monroe and I can tell you that they almost match perfectly. actually I think the throttle body has slighly bigger opening. IMO unless you're going to be running 9's in a Hot Air set up that throttle body is more than enough to get you into the 10's. I agree with Jerryl that money could be spent elsewhere like making that 4.1 block stronger since it will come apart at 500hp anyway. The only down side of the stock draw through system is the lack of turbo options.

 

[UncleDave]

You can have your stock TB reworked, this is who did mine
84
He did a great job and the turn around was fast

I looked him up before. Actually, these look like the ones GBodyParts sells, including the turbo/intake adapters; the pictures are identical.

Also, and someone can correct me if I'm wrong, but if sized incorrectly the throttle body can cause a pressure drop (vacuum) between the TB and the compressor inlet. Only a couple of psi could make a big difference in power. And especially with it being so close, there's the problem of throttle blade position affecting the filling of the compressor wheel. How about moving the TB further from the turbo? Would a few extra inches serve to stabilize pressure? I've actually thought about repositioning the throttle body to the other end of the elbow, to move it away from the turbo.

EDIT: Just saw Boostmaster's post right after submitting this... port matching might give the biggest bang for the buck because of how the TB is mounted directly on the turbo. I just wonder if there would be any advantage from simply repositioning the TB. As long as the turbo is getting enough air to operate efficiently at a desired boost level, there's probably no more gains to be had by going bigger than that.

 

[boostmaster]

Just took some measurements. The stock throttle body inlet is 62mm at the maf pipe opening. The stock throttle body outlet is 57mm. By comparison the stock turbo compressor inlet is only 52mm. The figures that you quote for the stock intercooled throttle body is for the inlet side only. there is not enough material in either stock throttle body to bore out to 70mm on the compressor side. Actually the stock 84-85 throttle body is larger in diameter than the intercooled ones and should be more than enough in most cases.

 

[UncleDave]

Where can I find information regarding the inlet diameter of specific compressor housings? Can't seem to find anything on the vendors' sites.

I think the turbo I eventually choose is going to determine my throttle body requirements. I have lots to do even before selecting a turbo.

On a slightly related note: For a while, Precision had newer technology TA-style turbos for sale, i.e. TA6265, etc. I think I saw a thread on them from back in April and there was much ballyhoo regarding lack of hot air support, stemming from a lack of direct bolt-in replacement. If AJ has solved the carbon backing plate issue, a TA-style incorporating modern technology would seem to be manna falling from the sky, wouldn't it? It would need a little adapting, but the basic configuration is there. Wonder if there are still any floating around the market.

 

[boostmaster]

Where can I find information regarding the inlet diameter of specific compressor housings? Can't seem to find anything on the vendors' sites.

I think the turbo I eventually choose is going to determine my throttle body requirements. I have lots to do even before selecting a turbo.

On a slightly related note: For a while, Precision had newer technology TA-style turbos for sale, i.e. TA6265, etc. I think I saw a thread on them from back in April and there was much ballyhoo regarding lack of hot air support, stemming from a lack of direct bolt-in replacement. If AJ has solved the carbon backing plate issue, a TA-style incorporating modern technology would seem to be manna falling from the sky, wouldn't it? It would need a little adapting, but the basic configuration is there. Wonder if there are still any floating around the market.

You have mail!!!

 

[UncleDave]

Thanks Pete for helping me wake up a little. Must have had too much turkey last night. Looks like even with a 6262 a stocker ported to 62mm would work fine. The 4.1 is a slightly different animal though, but it should turn out to be a torque monster.

Next issue: I need to find someone nearby who knows how to weld...

 

[charlief1]

You're gonna laugh Dave but check the local college. If they have a welding course I'd bet the instructor would do it in one of the advanced classes.

 

[Hot Air]

Hot Air guys and gals, check out "Met Jamie at BG" in the E85 Technical Forum! Jamie and husband Karl went 10.40 at Nationals last month with stock hot air intake. She was running E85 to cool the compressed air. Her car is far from stock running parts developed my the couple. Jamie tells me they port-matched the intake to the heads and that the intake had not been cut apart or been ported. Check it out. The car has since run 10.30's!!!
Conrad

 

[UncleDave]

Jamie and Karl's accomplishments get partial credit for my motivation to get back into hot air. The choice to run E85 is no doubt a major factor in their success, but that's one component I must live without. I'll have to ask Santa for an E85 reseller near me.

 

[Boost231]

Hot Air guys and gals, check out "Met Jamie at BG" in the E85 Technical Forum! Jamie and husband Karl went 10.40 at Nationals last month with stock hot air intake. She was running E85 to cool the compressed air. Her car is far from stock running parts developed my the couple. Jamie tells me they port-matched the intake to the heads and that the intake had not been cut apart or been ported. Check it out. The car has since run 10.30's!!!
Conrad

Really she went 10.30's now. Last I heard it was 10.55 at BG and 10.48 at her home track ending the season due to weather.

 

[boostmaster]

Jamie and Karl's accomplishments get partial credit for my motivation to get back into hot air. The choice to run E85 is no doubt a major factor in their success, but that's one component I must live without. I'll have to ask Santa for an E85 reseller near me.

Though E85 is just one component in her success it's not the total solution. After all isn't E85 just multi-port alky injection? And isn't it also just a cheeper solution to the price of race gas and octane? So theoretically with the right combo and proper tuning E85 is not the end of all solutions to go fast, it's just cheeper to do it with E85. I would go further and say that the same accomplishments could be done with race gas and alky with the proper tune. But as I have found out with that combo there is a fine line between suppressing knock and raising a fuels flash point so high that it won't burn enough to make power. So again it's all in the tune.

 

[UncleDave]

Though E85 is just one component in her success it's not the total solution. After all isn't E85 just multi-port alky injection? And isn't it also just a cheeper solution to the price of race gas and octane? So theoretically with the right combo and proper tuning E85 is not the end of all solutions to go fast, it's just cheeper to do it with E85. I would go further and say that the same accomplishments could be done with race gas and alky with the proper tune. But as I have found out with that combo there is a fine line between suppressing knock and raising a fuels flash point so high that it won't burn enough to make power. So again it's all in the tune.

Using E85 allows you to take alky out of the equation. One less parameter to worry about, and there's advantage to keeping things simple.

With the IC, I tune with a scanmaster and butt dyno, which is immensely fun but not very scientific. I think tune is more critical in a hot air application. Not something I want to mess up, and anything that allows better control of tune is advantageous in my book. How many of you tune with an XFI vs the 86/7 ecm w/TT/PL? Before GM went to the air-to-air IC, they were experimenting with alky/water injection. One can only assume it would have been applied via computer control. Whether it would have been programmed into the ECM is anyone's guess, but there would be advantages to having the same computer control fuel, spark, and alky. Just a thought.