i am building another tpi for my s-10. it currently has a 305 tpi in it (bought it that way). i am now building a 355. i have a ported/polished upper and lower intake manifold, ported/smoothed slp runners, double hump 461x heads, 4.11 gears, built 700r-4 tranny. however i dont wanna get the throttle body to big. i would think the 52 would be ok- but those heads i have do flow pretty well and i am pretty sure i have the extra tpi i bought opened up pretty well. i just dont wanna overdo it by getting the 58mm and wishing i hadnt gone overboard. any help is appriciated.

p.s.
i am heading to the junk yard this afternoon- i was there yesterday and there was a late 80's tpi camaro that they had just gotten. let me know if anyone needs anything and what you will pay- and i will see if i can get it. i'm not looking to make any money- i just know that sometimes tpi stuff can get expensive on ebay. if you wanna check my feedback on ebay- here is my name- that way you know i am legit (*SP?) bumpnzx3

 

I would have to say 58mm is a bit overkill for you setup. Even the 52mm is up there....the 48mm will do the job, but you may see some rpm out of the 52mm. Just my opinion.

Welcome to the boards.

 

i was thinking the 52 would be the way to go. is it cool that i post here even though i dont have a camaro- just the engine that goes in one?

 

I don't see why not>>> When I first got here I only had my Monte SS with a TPI under the hood. I didn't buy my Camaro till afterwards. Heck we have Mustang owners who are regulars here. Most of them are good people too, just have a few morons. Just make sure you read the rules. THey will keep you out of trouble. Here is a link to the "RULES" Have fun and Happy Hot Rodding.https://www.thirdgen.org/techbb2/sho...hreadid=143760

 

This is a good question. I just got done talking my old man out of a 58 mm throttle body. The best way I could find to explain it to him was like this. Pretend you have a cup of soda. If you use a real small straw, you have trouble getting all the soda you want from the glass. If you had a straw that was an inch in diameter your lungs would not have enough cpacity to get the soda all the way up the straw. If the straw was the right size and matched to your lung capacity you would get a lot of soda quickly. Same goes for a throttle body, it is the motors straw for air. How big of carb would you put on that engine? If your answer is less than 700cc than stay with the stock TB. If it is between 700-900 go with a 52 mm. If it is over 900 go with a 58mm. hope this helps.

And BTW an S10 with TPI in my book is tottaly cool here. My dads car is a 77 vette I converted to TPI. I myself have a 91 GTA. If you need any help tuning your truck I do proms. I could give you some pointers.

 

cool- thanks

my dad had a 1987 gta (i think it was an '87) it was pretty cool- i loved the computerized dash. i would have liked the car a lot more had i been old enough to care about cars- he had it when i was about 7 or 8

 

TB's are expensive, why not just cut the center divider out and make another throttle-blade like this?

 

52mm I would think should suffice

 

You're kidding, right? That looks totally hacked up and crooked. I don't think you could even physically make a throttle blade that would fit in it and work properly.

 

I think you can throw that one away now.

 

No thanks, I'll keep it. I already have it patched up now.



That doesn't sound very encouraging, but I think I can and I've already started.

 

aaaaaalllllllrrrrrriiiiigggghhhhtttttyyyyy ttttthhhheeeennnnn

 

Wow, that looks really professional. What is the putty on the inside of that TB?

 

The flow on those heads is anything but crazy.

I'd stick with a 48 if I were you.

Oh, and nice mono-blade thingamabob. I can't wait to hear all about the first time it jams open.

 

... AS&M makes the same solid tb like that.. and i think they own the rights... i was thinkin about it and made one out of plastic... so i guess u got a good idea there... it would flow alot... go try it i guess... just match the gasget (if u can) and the plenum... have fun man

 

just curious ?!? is that for your 305 ?????
I seen a monoblade setup ( 1000 cfm ) From what I have learned on here from all the experienced members ..... that is overkill even for a 350 !

JMO

L8R

 

Yeah, the AS&M unit is something like 1000cfm. That's nuts!

 

here ya go... holla http://azspeed-marine.com/marine-11.html

 

I guess you more senior guys are going to make me bring up this post

https://www.thirdgen.org/techbb2/sho...+throttle+body


Read the whole thing and understand why for your combo with the 355 will be just fine with the stock TB...

Good luck

 

I think it's funny how everyone says that since the stock TB is good into the 12s you won't see any gains in going bigger. I disagree completely.

I've also heard people apply the 'straw' theory when comparing restrictive parts of the TPI. It's not that simple.
Bottom line is, even though an engine is basically an air pump our engines are not straws.
IF this theory were correct then we would only see a gain by replacing the most restrictive part. If the stock exhaust manifolds are the biggest restriction then why did I see a gain from a cat back exhaust? And another gain from a cold air intake? These were before I got headers. If the runners are a bigger restriction than the manifold then I would be wasting my $$ to replace the manifold first because I would see no gain right?? Wrong.

Some of you hit it right on the head by saying that a TB isn't the best mod for the money but that doesn't mean it will not yield a gain like some of you claim.

TPIs-10: If you are set an getting one then the 52mm should suffice.

 

I will not argue with you about who's theory is correct you may believe what you want to, but this is the way it works. Your cylinders are giant syringes on naturally aspirated engines. During a single rotation you have a certain number of cylinders going down and a certain number going up. The cylinders going down are suctioning air into the motor. If the pathway for the air is bigger than the combined capacity of the cylinders going down than the air velocity coming into the cylinder dies and it does not completely fill. Think about a syringe. It would not work real well if the end of the syringe was bigger than the rest of the syringe body. Comparing the manifolds to the intake is like comparing apples to oranges. You want to push exhaust out as quick as possible this will speed up the engine. The right size exhaust also applies though. Again you want to accomplish velocity, this way you can more efficiently empty the cylinders of burnt gases. If your exhaust system is to big then the gases are not suffecietly pushed out of the cylinder. The gases just kind of swish around in the big open space and take up room that could be used for a new intake charge. IF the straw theory is not correct I guess I may want to rethink my career

 

I should have clarified myself. In one sentence I was referring to exhaust manifolds and the other the intake manifold.

I can use the same examples though.
On the intake side: If the runners are the most restrictive then an intake manifold swap would yield zero HP gains according to you. You WILL see a LARGER gain by replacing the most restrictive part, however, almost any mod will help.

Same goes for the exhaust side. The stock exhaust manifolds are more restrictive than the factory cat back exhaust (when compared to aftermarket items) so I guess if I changed my cat back without changing exahust manifolds I would see zero gain right?? Wrong again. Headers are a much better mod for the money though.

My point is that I've heard so many people say that the stock TB is good for 12s and therefore it doesn't need replacement until then.
I guess since there are a few cars in the 12s with stock heads (not many) or stock exhaust manifolds (even less) then those parts don't need to be replaced either right?

 

Not that it matters but I never stated zero gain or positive gain. I also never commented on things being restrictive. What I did state in an effort to answer the original question, is that going to big can actually rob your engine of power by killing the velocity of air through the motor. I would like to see TPIs-10 make a succesfull street machine, because personally I think TPI street machines are pretty cool

 

Ok, let's forget all about theory and just go by numbers.

When GMHTP (or was it CHP?) tested a 58mm throttle body on Tom Keliher's somewhat-modified L98, they lost 1 or 2 tenths in the 1/4. Let me rephrase it: Tom's car ran 1 or 2 tenths SLOWER with a 58 compared to stock.

I don't have numbers with a 52, but ANY gains whatsoever is highly unlikely. It may not slow you down as much as the 58, but it sure isn't going to help a hell of a lot if at all.

I've got a buddy with a super-rammed L98 Corvette. He had the same setup as a lot of Vette guys, and had similar results. Even with no PROM tuning (and some very nasty A/F ratios) he pulled some great dyno numbers:
http://personal.tmlp.com/scorp/vette...ine/pull-1.gif
Oh yeah, he had a 48mm throttle body.

Yeah, I know... this doesn't prove anything either. It's still something to chew on.

 

Well I would have say that your buddies results pretty much line up with the results I have experienced and my previous advice in this post.

 

No matter how well you port it, i dont think it's possible for the stock intake base to be less of a restriction than the TB. And especially on a stock headed motor as well, you are just not going to make the kind of HP that would warrant a TB. I am sure you'd go faster with a stock TB and an aftermarket base then you would with a TB and a stock base.

Beyond that though, i don't place much merit in the 'velocity through the TB' argument considering the large ductowork it feeds from, and the large plenum that it dumps into do a fine job of slowing things back down. Not that big TBs are a good mod idea. Just that the velocity argument doesn't seem grounded in science.

 

Actually if you would like I could give you the exact fluid dynamics equations used to figure the runner and plenum volume. I also could give you dyno sheets the exemplify each situation and what trade offs are made between horsepower and efficiency. I just figured that may be a little involved for a chat forum made to exchange ideas. Aprime example of air velocity producing horsepower are the vortec heads. If not science than what otherworldly phenomenon enables measly 170cc runners to produce healthy horsepower numbers from 350-450 on a regular basis.

I could also use some enlightening on what actual mechanical mechanism draws air into a naturally aspirated engine.

 

After being here for a while I should of known that giving advice in order to help a fellow hot rodder comes with consequences. Well if you prefer not to take my word for it ,for reasons I do not know. Maybe you will take the word of some other sites and books. Here is some light reading if anyone is really interested in tips that will really help you car perform better.

http://www.grapeaperacing.com/GrapeA...ntaketuned.cfm

If anyone is interested in a more indepth look to the subject. I have some books I can list also that go into greater detail.

 

That's good info. I've read it before. Unfortunately, it has nothing to do with a throttle body on a TPI car. Like Ed mentioned, the huge plenum volume is going to negate the effects of the throttle body on the rest of the system. The ONLY issue is whether the throttle body can supply enough air, and there's more than enough math out there to prove that the ~750 dry cfm that the throttle body can supply is substantially more than any mild 350 will ever require. Likewise, the port tuning issue is a function of the runner length, which extends from the intake valve, up to the plenum (and is 25" for those that care to do the math).

 

Where's the math?

 

Do a search. I'm not digging it up. It's been hashed out a hundred times.

 

so it's been posted before so it means it's true?

 

I have a better idea. Please enlighten me as to the function of the plenum in the intake of an IC engine? Perhaps someone has led me astray, but i've always thought it was there as a reservoir/buffer.

Oh, i get it. Velocity in the TB will help 'ram' more air into the plenum because of the inertia of the charge between the intake pulses. Neat idea, except the TB bores are pretty short, shorter even than the port in a head w/o an intake even bolted up so i doubt you're going to get much free inertial charging through the TB here. Especially given that the intake pulses have been overwhelmingly buffered by the plenum before they even get to the TB.

I honestly don't know if you were being sarcastic or not when you asked how air gets into an engine, but i'll review it anyway, perhaps you can show me how i am wrong (seriously, i enjoy being wrong)
Individual intake runners most certainly NEED good velocity to ensure a good inertial ramming effect as the valve closes to achieve maximum possible VE, and they get it because the column of air in the runner is constantly accelerating both in and out of the runner. Peak velocity in this column is i'm sure an insanely compex function, but i'd guess it happens shortly after the mid point of the intake stroke when piston velocity is greatest and the valve is just starting to close. This air then rides that inertia into the closing valve, thus forcing more air in then would have gone if te air had no stack to call a system all it's own. Then the valve closes and the column stops and actually 'bounces' back slightly as the columns inertia compresses it against the intake valve. It's that 'bounce' that gives TPI it's T, using the long runners to exploit SHM and use the return of that pulse to jumpstart the next inatke pulse. Thats why TPI works well right on it's torque peak and falls off quickly on both sides of that peak. You only get that help at the specific frequency that the wave returns at.

But like i said, this in and out game of intake pulses is buffered by the plenum so the action is going to be much more muted at the TB. I.E. Air does not stop and go at the TB, reversion is a much more subdued phenomena that far and buffered from the valves.

Hopefully we can agree on that much.

The tricky part then becomes the magnitude of the velocity's help on keeping air moving into the TB. Again, like i already said, the TB bores are very short even compared to the shortest runner intake and head combo you can think of. And the length of the column determines it's mass, which determines it's inertia. So you have a pretty low inertia, coupled with seriously buffered intake pulses. And the magnitude of the pulses is key. If you don't have strong pulses, then you don't need inertia to keep air moving to cover the rarefactory region behind the pulse.

And that last sentence is key. Velocity in and of itself isn't going to do anything for you. You'll always flow more with less of a restriction. The reason velocity is good in an intake/exhaust system is because you are trying to cover the peridoic nature of the pulses (or even take advantage of SHM as TPI or long tube headers do). Don't lose sight of the fact that accelerating air to get it through an orifice costs energy. So the less wasted velocity you impart on your airstream, the better. And since air most certainly is going to slow down when it hits the plenum, that extra velocity is in essence wasted. Unless it brings in enough extra air power) to make up for it.

But at the end of the day, since it's documented fact that running a bigger TB on a bone stock car is at worst an inconsistent and untuned few HP lost, and sometimes even shows gains, i think this whole debate is silly. It's like arguing the merits of an airfoil. I don't care what a flowbench says, nor do i care what fluid dynamics would predict as the best shape. I just care that it's worth all of 4hp and if you're really lucky and jesus smiles you might get 6hp. A 52mm TB on a stock engine with no tuning might cost you 1/2 mph and 2 tenths. Or you might pick up the same. The important thing to know is that the stock TB flows more than the stock runners, base, or heads ever will so replacing it before those just doesn't make sense.

Why did i waste my time with this argument then? Like i said, i enjoy being wrong. This velocity through the TB argument drives me nuts, but the way people just won't let it go makes me think that maybe i am missing something. Either that, or you guys are overestimating it's significance and are debating me on way too fine of a point (i.e. the airfoil analogy)

 

Actually it does state TB sizing and the velocity effects in the Helmholtz Resenator section. That section also supplies some simple math to get an idea on sizing a TB. Math is math and it does apply to our cars. It does not mater if the manifold is wet or not. Air flow is airflow. Realize I am not implying anything about horsepower because atomiztion and suspension does mater when comparing wet and dry manifolds, but right now the dicussion is about the physics of airflow through a motor. On a side note I have designed several intakes using Helmholtz equations and even though the plenum calculations may be off the rest of it works extremely well for air tract optimization.

So TPIs-10 I bet you have more information than you could possibly use or expected. Out of curiousity has any of this help you to make a selection?

 

BAM. Thank you, please drive through. I am now pretty well convinced you are playing pseudo-intellectual. Let me show you why:

'should not be higher than' implies you want to keep velocity down. If maximizing velocity was the key they would have said so. But of course they don't. Because wasting energy accelerating air in the TB will only cost you power.

 

This is so much fun. From the next section on plenums. Observe they say exactly what i did. The purpose of the plenum is buffer/reservoir. They even use the term 'slow down the (intake) gases'

Bwahahahahahahahaha

 

You want to keep the velocity at an efficient peak. To much restriction and the engine is starved for power and yes I agree uses to much enrgy pulling in air. Yes the plenum does slow the air down, but that should only happen after a completely fresh intake charge has entered the chamber. If the intake tract is to big, what you end up doing is swishing around spent gases. Maybe I missed something here but burning spent gases sure does not sound like a way to increase power. If you also read my previous post and the page on Helmholtz. They state that the equations do not quite hold up. Pseudo-intellectual or not try a dyno run with a 350 that has an oversized intake system. Peak power may go up, but all mid range will be lost. This works because once the engine reaches steady state complete cylinder filling can be accomplished by the momentum of the air at that RPM.

 

We're not talking about reinventing the wheel here and slapping a victor jr. 4 barrel manifold with a 1000cfm billet TB on it.Of course a ridiculously overkill intake setup will cost power. But, slapping a bigger TB on a stock engine has been documented as being far from the end of the world. While some people see a small loss, other people see small gains. Like i said, this is turning into the airfoil debate, it just doesn't matter. I'm not an idiot, and i don't think you are either (the razzing was b/c you did afterall act like a smarty pants posting reference materials that only backed up exactly what i was saying the whole time). So this isn't about the basic concepts, we're both familar with that much apparently.

To me. it all boils down to velocity in the TB isn't some magic phenomena that is key to making power. Of course in the grand scheme of things you want everything sized properly. I said that much too, in fact it was my main point in my first post (that a TB is useless compared to the base, then runners) I just don't think it's fair to act like a bigger TB is necessarily evil and going to take away significant power.

I would even go so far as to say that if you HAD to pick one piece of the intake to oversize, the TB would be the least significant thing you could pick (i.e. bigger runners, or bigger heads, etc are going to seriously and very directly impact cylinder filling. As pointed out, the TB and the velocity there is pretty well buffered from the heads, so it isn't going to have as much of an effect.) If you can agree to that much then i think we're down to splitting hairs over a few hp, which is a pretty insignificant margin to argue over any more.

 

I agree with this guy... and who said I wanted to run 12's? I sure didn't. I plan on going much faster than that.
I have heartburn with the thought of spending anywhere from $200 to $400 for a new TB when there is so much potential there for almost nothing.
My monoblade should easily flow over 1300 cfm, but more importantly I'm looking for a big increase in air density inside the plenum and runners.... as in zero vacuum at WOT.
Any math that figures cfm @ 1.5"hg I'm not concerned with at all. I'm concerned with the math that will tell me the change in air density by running my big TB.

I'm also increasing the size of the plenum as well and removing all of the dividers in the plenum.

 

Hay ....sorry I gotta get in this post THIS IS REALATED TO THIS POST !!!!!!!!


While I have all these engine smarties together ( not being smart *** )


just say ..........
I take an over sized TB lets say ..... that 1000 cfm mono .....
bolt it to a plenum that is port matched for lets say 52 mm ...
then go to a stock ported base . 48mm

I am just wonderning .... with this reduction along the way .....am I createing a ventury effect , thus speeding up the air , increaseing VE? Or is there no hope of accomplishing this disired effect because of the Plenum acting as a buffer ?

if I can't get this effect ......why enlarge the TB at ALL ? I am just curious ( seriously) what could justify getting one unless you are running some nastly horses that just gulp up air ?

this is a great thread !!!! I am more enlightened than I ever was in school !!!! ( for real)

 

No, smart ***. The math makes it true. The fact that I work for a living means that I'm not spending the time to go dig it out of the archives when the search button on your screen works just as good as mine.

 

Sorry about that. Whenever I search on this board all I find are the same type of discussions like this one and nobody ever agrees on a good final answer anyway.
I have seen the formula that uses engine cubes & RPM to determine CFM requirement, but this information is useless to me because I don't think it really applies to a running engine, just maybe an air pump.

I mean you can have
A: 700 CFM @ 2"hg pressure drop
or
B: 700 CFM @ 0.1" hg pressure drop,

and they are completely different to the engine. This is mainly because case "B" has many more oxygen molecules than case
"A".
This is a big difference in density, though the actual volume of air is the same.

get it?

 

I know that my car is not stock (383, AFR 190 heads, ZZ9 cam, headers, aftermarket intake manifold, exhaust) but I'm still running the stock TB. I have an Accel 58mm TB(1000 CFM) sitting in my garage that I was going to install along with the SuperRam plenum and runners (don't have those yet) and 24# injectors. I guess I could throw it on and do a comparison. Maybe I'll put the injectors in with the stock TB and do a test then swap the TBs and retest. Not sure how scientific this will be cuz I'm not going to do the tests on the same day but at least it'll be 2 more cents to this thread.

 

Yeah, I get it, but I think you're trying to split hairs.

Here's the math from Grumpyvette:

Grumpy made more than enough best-case assumptions that allow for a HUGE margin of error way beyond any difference you'll ever get from a pressure change, and still show the complete and total uselessness of going with a bigger throttle body.

 

I agree Ed! and I am sorry for acting like a big smarty pants. It really was unintentional. Many times here I get frustrated because these threads become useless because a debate gets out of hand. I just wanted to post some useful info that people could compare are conversation with so they also have something to base their thoughts off of. I also agree that a large throttle body is not the worst thing you could do.

 

To answer TPIs-10's question. Remember the guy who started this thread?
Stick with the 48mm thingamabob, honestly, it will flow plenty of air to feed
your engine well past 8,000rpm if you can get it to crank that high.

 

I agree with him and that's exactly why I'm not spending money on it.

Jim, if you would do a test for me, I'll figure out how much air density you're losing because of the entrance to the plenum.
All you have to do is hook a vacuum guage up to the plenum (power brake port or FPR port) and mount the guage so that you can see the vacuum reading at WOT driving at high RPM in 2nd gear.
The reading will probably bounce a bit because of the pulsing in the plenum caused by the intake valves closing, so go by the higher of the vacuum number. I'm guessing you might get at least 2"hg vacuum at full throttle.
Let me know what you have and I'll calculate the theoretical power loss caused by your TB restriction.

 

In my opinion, given a dry flow manifold,
the only place you actually want any kind of venturi effect going on is around the intake valve seat, and then only a slight effect.

The idea of the venturi effect is to create a pressure drop... which happens to be great at atomizing fuel in a carburetor.
again, just my opinion on that.

 

I'll get back to you this summer when my car isn't in hybernation. I'll do your vacuum test with my 52 and with my stock 48. I'll even do one better and I'll bring them both to the track with me and I'll swap them between runs. When I do the vacuum test I'll be blocking off my vacuum cannister too, because I'd hate for that to give me an artifically high plenum vacuum reading.

 

Well actually just the vacuum reading would work for me.

There would probably be very minimal difference between a 48mm and 52mm TB's.... maybe not significant.
The track test would only be conclusive if the optimal tuning was found for each TB to account for the air density difference.
Also the TPS would need to be readjusted along with the Acceleration Enrichment. Otherwise you could get a bit of a flat spot when you hit the gas pedal because of a more rapid increase in air-flow and air-density with the larger TB.