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Help!! 52 mm Throttle body




I'm thinking of getting a 52mm TB next
in my quest for HP to down my 1/4 mi
time. I have an opened up air induction
(SLP's claw), so I want to get even more
air to the engine.

But, if I get the 52 mm TB, will that
extra air lean out the engine too much?
Will I thus need a custom chip since
my Hypertech is too close to stock?
Or will I need an adjustable fuel pressure

Is there another mod that you guys would
do first if you were me? (other than
cat back--that I will probably do later)

I considered just the TPIS airfoil, TB bypass,
and MAT sensor reloc, but I'm doubting this
combo will do much for me. Maybe not even
.1 sec.


Well I'll put in my 2 cents worth. I put on a 52mm BBK and so far it's really not been an improvement the main thing that happens is that effectivly you reach wide open sooner! and the small throttle openings are harder to modulate. This translates into the cruise surges on the road under 75 and no more wide open power as the runners and plenum are too small! the only way you can use it is if you go to a larger (more flow) intake, base, heads, cam, basicly the whole nine yards.then it'll work better.
Oct 30, 2001
Glen Burnie, MD, USA
1986 Bright Red Coupe
Andy, I'm in the process of doing the TB bypass and the MAT sensor relocation right now (as well as the auxiliary fan and an open filter cover). I'll be heading to the track hopefully within the next two weeks and we can see what good those will do you.


Well I guess I should read what engine you have first! seem s like you have most of the goodies. about the only thing you could add woud be some high flow heads, Perhaps AFR's



I installed a 150 hp NOS kit and I can tell you this was the best bang for your buck investment in hp that you can make! My car RWHP is 363 with and incredible 427 ft. lbs of torque. The N2O kicks on at 3,000 rpms and off at 6,200 to prevent lean out, and the unit only is operational at WTO. I have added alot of other goodies but the N20 was the best, unless you can get a set of CNC ported heads from AFI and a cam to compliment it at a cost of about $2,800 if you do your own work.


Active member
Oct 3, 2001
Dublin, CA, USA
1994 Black/Black Coupe

Where do you mount the cylinder on a Corvette? How large?




NOS Tank

I have a 96 convertible and the bottle fits right behind the drivers seat with no problems, even with the top down I have alot of clearance, and room for 1 small suitcase! lol!



Save your pennies until you have enough to get a 4:11 rear gear. This will give almost as much bang for your buck as nitrous with far less chance of hurting your engine.
If you put on the 52mm t-body, the O2 sensors and the computer will keep the engine running right. A change like that does not require you to change the chip. You will see little if no gains from the t-body until you port the heads and change the cam.



Nitrous: Nice idea but illegal in Maryland.

Rear gear: also very nice idea, if I wanted
acceleration at minimal cost, this would be
it. However, I don't want power at the expense
of destroying the fuel economy. Plus, the
extra rpms would wear the motor much more and
the wife would hate the extra noise.

Thanks for the info. You seem pretty sure
the 52mm TB would not help, how do you know?
Do you know anybody that has tried it
on the LT-1? Or are you applying engineering
principles together with your knowledge of
the LT-1 and concluding that it won't help?
--I just don't know how restrictive the LT-1
intake is in stock form.

Anybody know?


Gone but not forgotten
Jan 30, 2001
Hermosa Beach, CA
1987 Z51 Silver Coupe
I've been told that Myron (Cotrell) based his manifold, the "Mini Ram" from TPIS (the one that Chris and I are running) on the LT-1 intake. You'll notice in our pictures of our engnes (Chris's '90), the intakes are noticibly shorter than the stock plenums/runners, it's more like the LT-1's.

_ken :w


Well-known member
Dec 11, 2001
Suffolk, VA
Red 96 LT4 coupe
Rear gears don't have much affect on fuel economy if you have a 6 speed.

With your stock 3.45 gears, and your .5 6th gear, normally at 80mph you would be turning 1818 rpms. With 3.73s (the largest size you can go with the stock carrier) you only turn 1966. This is assuming you have the same 25.5 inch tall rear tire setup as me (17in wheels with 285/40 tires)

If you shell out more bucks for a new carrier, and get 4.11 rear gears, at 80mph in 6th you are still only gonna turn 2166rpms.

So, for us 6 speed owners this isn't a big deal. Sorry for those automatic owners who turn close to 3000 rpms @ 80 with 3.73s.

I've talked myself into 3.73s for my next mod


Well-known member
Apr 17, 2001
Loxahatchee, FL, Palm Beach co
read this
"DO I NEED A 58mm THROTTLE BODY on my TPI 350 to get better performance"
I get this question about once a week in my E-MAIl

ok time for a math lesson, please try to follow along,(yes Im well aware some of you know even more than I do, but this is for the new guys)the stock throttle body flows about 670cfm,
your 350 in the vette has a stock cam that has about 210 dur and lets be even more generous and say the heads flow 210cfm and your TPI intake also flows 210 cfm (to keep things simple, trust me, your stock heads, intake and cam don,t flow that well combined) now that means that at a steady flow rate with all the ports open at max cam lift for 360 degress of engine rotation that possiable durring the intake stroke your flowing 210cfm per intake port, correct (again being very generous) now in a standard stock engine theres 360 degees available in an intake cycle if the valve never closes (bad for the compression stroke) so about the most those ports can flow if the valves open instantly and stay open the full 210 degs at max lift is 210cfm/360 degs x 210degs the cams open or about 122.5 cfm x 8 cylinders=980cfm but since those valves open and shut durring the cycle your only able tp flow at about 65% of the max for a flow rate of about 637cfmthat well under the stock throttle bodys flow,
lets look at it from a second angle, your TPI 350 spinning at about 5500rpm (where it starts to run out of airflow big time) if the cylinders fill completely on every intake stroke(which remember is every 2nd stroke)is 350cid x 5500/2=962500 cubic inches or divided by 1728 to get cfm=557 cfm
now even if we add a 30% better flow due to exhaust scavageing, and ram tuning the intake pressure waves and a more realistic 35% reduction in intake flow due to the valve needing to open and close ,(not being instantly fully open the whole time)thats still an average of (557+637=1194cfm+10%=1313/2=656cfm,is about max the engine can use and in the real world its slightly less in a stock engine, and thats not counting for airflow volume losses due to heat expansion or restrictive losses due to the screens on your M.A.F if you still have them and are not running a speed density TPI or the air filter restrictions or the catalitic converters partly screwing up the exhaust scavageing.
now for the good news, unlike a carb system that relies on air flow to carry the fuel air mix, EFI can and does run better with a max possiable intake pressure behind that intake valve, adding a 52mm or 58mm throttle body will effectively add slightly to your potential air flow and reduce the systems airflow restrictions and unlike a carbed system its extremely difficult to add a throttle body thats so large that it screws things up,so if you want to add a larger throttle body ,go right ahead, it may not help (on a stock engine) but its almost never going to hurt either, but after much testing Ive got to say, if your talking about a stock engine spend your money on a 383 stroker kit, better heads,a better flowing intake manifold, headers, and a larger cam in the 220-230 durration range before worrying about a throttle body restricting your hp!


Well-known member
Dec 17, 2001
Eaton Rapids, Mich
!985 ,blue coupe, 4+3 Z51
Grumpyvette, your absolutily right! When I started my quest for more power I did the same as most and investigate by asking questions. It always came back to the same thing, breathing capabilities . While I have an L98 and the LT1 is better in many ways ,they too suffered from the same problems. Depending on what you want , from just a little crisper response to tiresmoking monster , that is where you start to narrow down your options. Ken ended up with the monster motor , Chris ,(69myway) with another tire killer and myself with the 383 ,AFR ,TPI manifold and runners and ported plenum,58mmTB. TPI headers and most of the other induction tricks plus the BIG prom. My engine builder was the final desiscion maker when it came to my quest. Also the cam was a big item. 268/274 ,224/230 @50, 112/112, 506/506lift. Will make about 425 to 450 HP,and 480/500ftlb.:D


Well-known member
Jun 3, 2002
Parrish, FL, USA
1992 LT1 White Conv.
52mm TB

sothpaw, grumyvette's reply here sounds OK as far as the LT1 needing 637-656 cfm. But his flow rate for the stock TB sounds way off. I have read numerous places that it is 450-480cfm, and the 52mm is 750-780cfm. ck out this site for recommendations on TB's. There are others too.




You guy's really know your stuff, its amazing, hehe,, im a newbie, kinda,, i know, where everything is on my car, and what everything is called, and what alot of it does, accept, for my engine, hehe,,,

i have a few questions
on a 383,, do u upgrade a 350 to a 383?? or how does that work
I know u buy a kit,, and stuff
i know u can buy like better compress headers, or something like that,, and a better cam,,,

but what is this with a 383,, i mean,, how much does the best kit cost,,
can anyone give me a web site on this,,
i can do all the work my self
i own a shop,,, i have car lift, cherry picker, and just alot of kewl stuff to work with,,, my dad is a machiniest,, he knows how to rebuild a engine but he doens't know, how to boost horse power and just stuff like that,,, so, waht does the 383 consist of, do i still keep my block??, or what,,,,, need a site too,, please imput on this,, thanx,,, oh and one more thing, does,, RAM do good on a L98 i heard it does great,, and,, if so,, where can i find a site for that too,, i need some sties from u guy's,,, like what is TPIS i hear that alot, is that a site?,,

i know thats alot of quetions kinda,,, but thanx

Alex D

Well-known member
Jun 12, 2002
Greensboro, NC
2004 Coupe A4, Mag Red II
Thanks !! I almost bought one ....



I installed a TPIS 52mm TBI and I felt a change right away

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