do you need a dual 58mm throttle body on your TPI?



do you need a dual 58mm throttle body on your TPI?

Postby grumpyvette » October 1st, 2008, 9:36 am

I get asked frequently if installing a larger than the stock 48mm TPI throttle body will significantly help on a corvette engine, Ill save you some reading right off if you want, yes a 58mm can potentially increase hp if your engines highly modified and your still useing a stock 48mm throttle body but the restriction a stock 48mm throttle body represents is not as significant and the gains to be had are not that large in most cases, your intake manifold and cam plus your heads are the major restrictions. the stock 48mm throttle body flows about 700cfm and has more than enough flow to support about 475hp-500hp, bored to 52mm it will support about 500hp,-525hp, a 58mm can support about 600hp, but keep in mind theres lots of factors other than just throttle body size that determine potential hp

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Keep in mind even the factory 502 cubic inch big block used the stock L98 TPI throttle body size and made 500 horse power


yes a 58mm can potentially increase hp if your engines highly modified and your still using a stock 48mm throttle body, but its hardly a big restriction, and your probably going to gain more with other mods
using or modifying a throttle body to flow more than 1000cfm -1200 cfm like a 58mm twin bore potentially flows is a waste of money, heres why
the largest displacement sbc your likely to build is a 434cid, that requires a 4" stroke crank and youll be limited to about 6500rpm even with top quality parts if you want the engine to last any time at all, now you might not realize it but the time necessary to fill the cylinders gets limited very quickly at higher rpms and the volumetric efficiency falls off quickly after about 5000rpm simply because theres just not enough time to allow the cylinders to fill completely. at 5000 rpm theres 41.6 intake strokes per second, per cylinder, by 6500 rpm its up to 54 intake strokes per second, per cylinder thats only 0.018 seconds for the intake port to flow into the cylinder per intake stroke. but theres yet another factor!!! thats the time for the full intake stroke!!!, while theres 720 degrees in the repetitive cycle and Ive given you a full 360 degrees worth of time, the truth is that your cam/engine combo, seldom allows anywhere near that duration!!!! even a radical race cam seldom exceeds 250 degrees in effective duration for port flow, so youll need to knock about 45% off that time, now your down to only about 0.012 seconds or less of effective flow per intake stroke per cylinder, is it any wonder the cylinder can,t fully fill at high rpms??
now the theoretical 434 were working with here even if it could fill its cylinders 100% at 6500rpm which is totally impossiable at that rpm would require 434 (the displacement) x 3250(the number of intake strokes)=1410500 (the full 100% in cubic inches /1728(to change to cfm) = only 816cfm.... now even if you could ram tune the exhaust and intake pulse perfectly and get the cylinders to pack the cylinders to 120% (a total impossability without a supercharger or turbo) thats till only 979 fcm
but in the real world your volumetric efficincy falls off fast after 5000 rpm with a 4" stroke and youll be exceptionally lucky to pull 80% efficiency at over 5000rpm
drop your displacement to a more comon 383 and your rpm limit to the fairly comon 6500rpm and youll drop even the theoretical air flow requirement to below 875cfm

http://users.erols.com/srweiss/calchpaf.htm

http://users.erols.com/srweiss/calccarb.htm

heres the ramjet ZL1 454
http://www.sallee-chevrolet.com/ChevyBigBlockV8s/ramjetzl1.html

viewtopic.php?f=55&t=1509
http://www.summitracing.com/parts/sum-227702
yeah you might not believe it but it got a stock 48mm twin bore TPI style chevy throttle body feeding that 454 engine, do you think chevy would do that if it was a significant restriction to hp production??

the restriction is not the throttle body its the port size, valve size and flow the heads have and intake manifold runers restriction,and cam lift and duration... install an intake manifold,cam and heads that can flow 300cfm and the 58mm aftermarket throttle body will still effectively feed the engine, remember that while even 300cfm ports at full flow only pull air about 250 degrees out of 720 degrees in the cycle and are spaced 90 degrees apart, that means that 1000cfm can feed all 8 cylinders a full 833cfm they could in theory flow ,and that 300cfm per port can support roughtly 600hp
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: do you need a dual 58mm throttle body on your TPI?

Postby grumpyvette » October 15th, 2008, 5:12 pm

OK IVE JUST GOT TO ASK?
why would you buy a 52mm vs a 58MM throttle body????
now PLEASE don,t get me wrong,
the 52MM has a nice improvement in air flow over the stock throttle body, but in most cases that extra air flow is not used, especially on a mild engine or one with stock gearing and displacement, and the 58mm won,t in most cases increase the performance, and yes IM well aware from testing that the MAF sensors and the intake manifolds , and heads are the big restrictions, and that with out inproving those areas the stock throttle body works just fine.
BUT NEITHER WILL THE 58MM HURT a damn thing EITHER??
I tried BOTH on my 383 with BOTH the TPI and STEALTH RAM intakes, (I borrowed a friends 52mm to test) and there was no real difference untill I was up in the 6000rpm range, and even then the difference was minor, but again WHY buy the smaller unit, that could potentially be a restriction with future mods done??
its NOT like a carb, you won,t get a big loss of throttle response, in fact I could detect ZERO difference once it was correctly tuned) or for that matter experience any down side to the larger unit provided of course your tuning skills are decent.
and before you guys get crazy, do some research!
I don,t remember ever seeing a dyno on anyone elses engine EITHER that showed a LOSS to the larger unit, just a few that showed no IMPROVEMENT in a particular application, and if your thinking of pointing out a lack of throttle response thats been repeatedly shown to be due to tunning issues like low fuel pressure, too small of injectors,or the TPS voltage was off the mark, the IAC was not set correctly or the ignition timing curve was not ideal, or in a few cases the compression ratio was to low for the cam selected, get the LCA or duration wrong for the application and AIR FLOW REVERSION in the runners CAN cause problems, like a bog when you transition from idle to W.O.T. almost instantly, but in no case IVE seen was the extra potential air flow a problem, especially once you realize that the plenum/ports carry only AIR, and the fuels injected in the last 4 inches of the runners

BTW
http://www.sallee-chevrolet.com/frame.html?/sales.html

RAM JET 502 - FACTORY FUEL-INJECTED BIG-BLOCK POWER
P/N 12499121 [Old P/N 12497323]
The recipe is simple; one part attitude, one part driving perfection, one part leading factory technology, and five hundred and two parts hungry rat motor. Ram Jet 502, you either have one, or you want one! When the idea of an all new big block fuel injection system first came up, we all thought it was a good one. When it was proposed that it be integrated with our 502 crate engine, we thought someone had clearly lost their mind. Who could possibly need the awesome, flat, broad torque curve only available with a long runner dry manifold? And who would want the neck-snapping throttle response of MEFI 4 controlled port fuel injectors? And what would be the need for aggressive tunnel ram styling? But then we remembered we’re not building 100 mile per gallon, 0 to 60 in a week, eco scooters. We’re in the hot rod business! So we called together engine management system experts from GM Powertrain, our own GMPP engineers, and fuel injected race engine builder and GMPP Pro Mod racer Harold Martin. After some great discussions, a little debate, a lot of late nights and 50 gallons of coffee we had an intake manifold design like no other. By leveraging leading fuel management technology, numerous production developed components, the industry standard MEFI 4 controller and the great Ram Jet name from the 50’s, the Ram Jet 502 is reality.
The new undisputed heavy weight champion, the Ram Jet 502, makes 502 horsepower at 5100 rpm and 565 ft.lbs. of torque at 3200 rpm. The instantly throttle responsive Ram Jet 502 drives like no other big block you’ve ever driven. With over 500 ft. lbs. of torque from 2,200 to 5200 rpm, the Ram Jet 502 is a tire shredding monster making more torque throughout its operating range. This is possible because Ram Jet has a larger plenum and runners than would ever be possible in a carburetor application. This means greater intake efficiency and greater torque without sacrificing drive-ability. The Ram Jet manifold is so efficient that we’re able to make all of this horsepower and torque with a production L98 throttle body assembly, you know, the one that Fire bird and Camaro owners always replace when trying to make more power in their 350 engines. It’s all about airflow quality, velocity, and fuel and spark management. You’ll just have to drive one to appreciate it. If the one-second cold starts, no stalling, instant throttle response, and the solid pull from idle to red line don’t convince you that a Ram Jet 502 is for you, then maybe you would be more interested an a competitor’s futuristic dream of a 100 mile per gallon, 0 to 60 in a week, eco scooter or a good old fashion bicycle for those weekend events to impress all your friends at the local hot rod club or for those weekend cruses out on the highway to impress everyone else on the road.
The Ram Jet 502 is designed for ease of installation needing only 12V, ground, fuel feed and fuel return to run. Included are an instruction sheet, service manual and diagnostic tool for ease of installation and service. As with any GM Performance Parts Ram Jet engine, an in tank fuel pump is recommended to avoid possible vapor lock. See instruction sheet for fuel pump recommendations. Also included is complete throttle linkage that accepts your production throttle cable and transmission cable. Includes pre-programmed MEFI 4 ECM and wiring harness. This revised electronic and closed loop system gives a much smoother idle and better performance then the MEFI 3 ECM system it replaced.
The Ram Jet manifold stands eleven inches tall as measured from the front and rear “china wall” on the cylinder block. That’s just half an inch taller than a typical single plane high rise manifold, Holley carb and air cleaner combo.


RAM JET 502 TECHNICAL INFORMATION
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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those TPI throttle body air foils

Postby grumpyvette » May 4th, 2012, 3:10 pm

I frequently get asked if the throttle body air foils are worth the money?
the first thing Id point out its theres several versions and some can be potentially dangerous to use, because theses small components that can come loose under rare conditions but when they occur they can damage the engine. ID suggest you avoid the types that use a bolt that screws in from the front like the black plague

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http://www.summitracing.com/parts/sum-227702
summit sells a 58mm throttle body, obviously youll need to verify it fits and works in your application
read this link
https://www.youtube.com/watch?v=S_ni39iwAys

http://www.iroczone.com/2009/10/install ... e-airfoil/
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IF you find your throttle body is starting to wear and the throttle blade shaft binds or leaks air or the TPS sensor seems to bind, Ive had new bushings and throttle blade shafts installed in older TPI throttle bodies ,the cost locally was at that time parts& labor near $170 Id never do it again, the BBK 52mm-or 58MM throttle body seems to be at least to me a better deal in every respect.
now I have had my bbk 58mm throttle body on my 383 , used both on an extensively ported TPI and Holley stealth-ram intake, both as delivered and later with several custom plenum designs , and after using it id be hesitant to go back to a factory throttle body , it just seems to operate better and while it may not be a significant increase in power it looks better, it operates smoother and I'm sure it flows more air. keep in mind the throttle body's basically an AIR GATE and while you may not need its full potential, its not in control of your engines fuel/air ratio control, to near the extent a larger carburetor on a stock carb intake would be, simply because the computer controls the injector pulse duration and sensors control the fuel/air ratio, and the TPI plenum and runners are restrictive, so theres just no way adding a larger throttle body hurts mid and upper rpm power, yes it might slow off idle responsiveness very slightly but if your building a kick-butt, performance engine just the upgraded cam duration already does that to a larger extent.also notice the 58mm throttle body has the air foil machined into its design
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this type of air foil thats retained by the plastic air tube and worm gear clamp, rather than a bolt in the air foil body is far less likely to cause engine failures
http://www.jegs.com/i/Holley/510/120-140/10002/-1
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GOOD DESIGN ABOVE
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POTENTIALLY BAD DESIGN ESPECIALLY IF NOT INSTALLED CORRECTLY

IF you do install one of these air foils (LIKE THE PICTURE ABOVE) that are retained to the throttle body with a bolt be DAMN SURE you use GREEN LOCTITE on the BOLT THREADS , Ive seen several of those come apart over time, get sucked into a runner and do really nasty things to the valves and piston of the cylinder it fell into
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this extra 2 hp looks like its hardly worth the effort but its basically semi-free upper rpm hp, and rarely causes problems if the air foils properly installed

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heres the stock throttle body with no air foil to smooth air flow
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the better aftermarket throttle body designs come with a built in throttle body air foil and MUCH BETTER FLOW plus TWIN 58 MM bore size that easily supports 550-600hp PLUS hp

I just spent a couple hours helping one of the guys I know pull the upper engine off on his TPI corvette BECAUSE he FAILED TO USE LOC-TITE ON THE AIR FOIL RETAINER BOLT THREADS, the engine sucked in the air foil retainer bolt that came loose, after several years of use with no problems, , it worked its way thru the plenum and runner and wedged between the valve and piston locking up the engine and damaging the valve, cylinder head, piston etc. the heads, combustion chamber ,the heads valve seat, the valve and the head and intake gaskets will obviously need to be replaced the heads machined, and repaired, all because of the loose bolt being sucked into the engine , and he was darn lucky that the piston and block were only damaged cosmetically and can be polished and re-used, because he shut the engine off the instant he heard something obviously go wrong
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BETTER THROTTLE BODYS
http://www.summitracing.com/parts/SUM-227707/?rtype=10

http://www.summitracing.com/parts/BBK-1544/

http://www.summitracing.com/parts/EDL-3810/

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YES IVE INSTALLED A twin 58MM throttle body like this on MY custom holley stealth ram intake

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Ive always been rather amused at the guys who do swap to a 58mm throttle body on a stock or nearly stock tpi intake because the darn things are so restrictive even if ported that they can,t possibly use the increased flow, especially if sucking air thru a MAF sensor that flows about 670cfm
if your engine doesn,t have the necessary components to make at least 450hp, like decent heads cam and low restriction exhaust headers, your wasting your money on a 58mm throttle body on a nearly stock TPI

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before you go crazy over worrying about the difference in flow potential between a 52mm and 58mm throttle body, thats mounted on your TPI intake,to increase air flow and potential power, take a deep breath and remember the stock M.A.F. sensor, and both the stock cylinder head ports and stock T.P.I. intake runners and manifold are a larger restriction to air flow and power than the throttle body is more restrictive to air flow
related threads
bytor wrote:Came across this info while doing some research and thought I'd share.

http://www.hobracing.com/tech/tpi_flow.asp
TPI Intakes and runners

The following airflow tests were performed on the University of Northwestern Ohio's SuperFlow SF600 Flow Bench. All CFM values are corrected for airflow at 28 inches of water. Injector flow rates are flowed at 43.5 PSI on an injector flow bench using test fluid with same density as gasoline.

AirFlow

Stock TPI/LT1 48mm Throttle Body w/o airfoil -- 783.0 cfm

Stock TPI/LT1 48mm Throttle Body w/ airfoil -- 821.9 cfm

TPI/LT1 52mm Throttle Body w/o airfoil -- 848.9 cfm

TPI/LT1 52mm Throttle Body w/ airfoil -- 898.8 cfm

Stock 98 Camaro 3800 II Throttle Body -- 554.3 cfm

Stock TPI Bosch MAF sensor w/ screens -- 517.8 cfm

Stock TPI Bosch MAF sensor w/o screens -- 658.4 cfm

Stock 87 GN 3.8L Turbo AC MAF sensor w/ screen -- 584.2 cfm

Stock 86 2.8L AC 5-wire MAF sensor w/ screen -- 576.2 cfm

Stock 96-up AC 3100 V6 MAF sensor w/ screen -- 616.4 cfm

Stock 96-up AC 3100 V6 MAF sensor w/o screen -- 670.7 cfm

Stock 94-up LT1 MAF Sensor w/o screen -- 719.0 cfm

Stock 85-87 Firebird TPI airbox mid piece -- 499.3 cfm

Stock 4.3/5.0/5.7 2bbl TBI complete -- 574.1 cfm (dry)

Stock 4.3/5.0/5.7 2bbl TBI w/o injectors -- 584.7 cfm

Stock 3800 vin L throttle body w/ screen -- 419.1 cfm

Stock 3800 vin L throttle body w/o screen -- 444.8 cfm

4bbl MPFI Holley Throttle Body -- 1287.6 cfm

Another source sent in these flow numbers

Flow and HP ratings for Throttle-bodies:

Flow (cfm) Max. NA HP
Stock 668 300
Stock w/airfoil 710 350
52MM w/airfoil 835 400
54MM (AS&M) 900 450
58MM 1050 500


TPI Intakes and runners flow rates

Stock intake manifold with runner
Stock....................198.72 cfm
ACCEL................213.52 cfm
Extrude/ACCEL....217.11 cfm
Super Ram............220.67 cfm

the stock TPI has a hard time flowing 230cfm even with minor port work, look here
most of this info is right off the accel,holley,edelbrock, and TPIS sites, add a little math and the results become much clearer!!!

Intake....... length ....... port in -- out
Stock GM Base--- 6.375"------ 1.47"- 1.96x1.2
TPiS base------ -6.125"------ 1.75"- 2.09x1.28
Accel base----- -6.125"------ 1.75"- 2.09x1.28
Holley base------- 6” runner 2.3”- 1.9”x 1.23 (2.337 sq inches)
Runners
Stock TPI----- -- 7.250"------1.470" round(1.70 sq inchs)
SLP ----------- - 6.625"------1.600" round (2.01 sq inchs)
Accel LTR------- 6.625"------1.615" round (2.05 sq inchs)
TPiS----------- 7.625"------1.660" round (2.168 sq inchs)
Mini ram -----3.5”
LT1 ----------3”

Runners (measured individually)
Stock....................203.17 cfm
ACCEL................242.02 cfm
Extrude/ACCEL...275.83 cfm
Super Ram............289.18 cfm
Intake manifold with 3/8 inch radiused intlet.............................222.45 cfm
Holley stealth ram ………..275cfm

Stock intake manifold with runner
Stock....................198.72 cfm
ACCEL................213.52 cfm
Extrude/ACCEL....217.11 cfm
Super Ram............220.67 cfm
Holley stealth ram …..275cfm

ACCEL Hi-Flow intake manifold with 3/8 inch radiused inlet.........251.51 cfm

ACCEL Hi-Flow intake manifold with runner
Stock....................215.83 cfm
ACCEL................232.53 cfm
Extrude/ACCEL....243.21 cfm
Super Ram............240.24 cfm

Extrude-Honed ACCEL Hi-Flow intake manifold with 3/8 inch radiused inlet ...............275.83 cfm
Extrude-Honed ACCEL Hi-Flow intake manifold with ACCEL runner ..............266.94 cfm
Edelbrock Performer RPM manifold (Stock)..........286.51 cfm
Edelbrock Victor Jr. ............275.24 cfm

HOLLEY STEALTH RAM
the HOLLEY STEALTH RAM FLOWS at 275cfm out of the box, and has the potential when matched to the correct heads and cam to totally out flow most other intakes available,can easily reach 300cfm with minor port work and costs much less
Stock…………………………… 275cfm
Ported…………………………..300cfm

Runner lengths
Stock tpi manifold 8” runners 11.25”, cylinder head 6” total 25.25”
Accel super ram manifold 8” runners 7” cylinder head 6” total 21”
Holley stealth ram manifold 6.26” ” cylinder head 6” total 12.26”
Edelbrock performer RPM runners 6” ” cylinder head 6” total 12”
Edelbrock vic jr , runner length 5.5” ” ” cylinder head 6” total 11.5”



Also interesting TPI mods. Not so sure I agree with the one on bumping up the initial timing.
http://www.hobracing.com/tech/tpi_mods.asp


Basic TPI modifications
Friday, May 23, 2014





Basic TPI Mods: by DEBBIES87

There are a few basic mods that should be done to any TPI car, I call these "entry-level" modifications.

1) Cut the air box open without letting air in the engine without going through the air filter & remove the additional plastic piece below the air box to get more air into the engine.

2) Modify the mass air sensor; remove the screens, & and if your brave cut down the fins.

3) Port the plenum (upper intake). There are two small ridges sticking up in the entry-behind the throttle body, remove these. The throttle body openings are already 52mm, so don't go crazy when porting.

4) While the plenum is off for porting, it is now a good time to get a adjustable fuel pressure regulator & a MAT sensor relocater kit. The Adj. FPR will aid in tuning, and the new MAT sensor will improve throttle response as well. The new LT1 style MAT sensor is placed in the air box instead of the plenum, this allows it to read cooler air and advance the timing accordingly.

5) Advance the base timing to 12-13 degrees. Note: the harmonic balancers on these cars tend to drift with age, adjust timing to where the car still starts good and doesn't detonate.

6) If legal in your area, gut the catalytic converter and remove the smog pump belt (85-87), or run a shorter serpentine belt to bypass the pump (88-92); you will need to remove the smog pump on the 88-92's to reroute the belt properly. Check local smog laws first.

7) On automatic cars, adjust T.V. cable (throttle valve cable), so that the car shifts out between 4200-4500 RPM under wide open throttle. TPI motor power drops off drastically after 4500-4700 RPM, they peak at about 4200-4400 RPM. No need to over-rev these motors.

8) Bypass fan relay to make fans come on manually, or install aftermarket relay to turn on fans sooner.

All together these mods should make the car perform like it should have from the factory, gains should be between .6-.9 tenths of a second from these modifications.




T.V


viewtopic.php?f=32&t=430

viewtopic.php?f=55&t=290&p=663&hilit=tunned+port#p663

viewtopic.php?f=55&t=1509&p=10297&hilit=stealth+ram#p10297

viewtopic.php?f=55&t=6546&p=20796&hilit=foil+throttle#p20796

viewtopic.php?f=55&t=1200

viewtopic.php?f=55&t=641&p=12915&hilit=foil+throttle#p12915

viewtopic.php?f=55&t=1231
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: those TPI throttle body air foils

Postby Big_G » May 5th, 2012, 11:35 am

Many years ago I had a 1992 'Vette, 6 speed. Pure stock. Went to the local 1320. Best it would do was 13.50's. Installed a tb air foil, K&N air filter in a cut-open air box, 1.6 ratio rockers and a Hypertech chip. Even cut out the MAF screens and trimmed the heat sink fins. Maybe mid 13.40's. What a waste of money. Goes to show Chevy did things pretty good from the start.
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