The debate has gone on for as long as I can remember.
Is a larger throttle body worth anything over the factory 48mm on a stock/mildly modified engine?
There's always been two sides of the argument and I suppose there probably always will. This thread isn't meant to throw fuel into that fire, but only to give you guys an idea of the differences between a stock LT1 throttle body and an aftermarket one as well as to share my experience with making the switch.
I'll start off by saying up front that I did NOT buy this throttle body thinking I'd pick up a bunch of power. I'm currently in the middle of a 396 LT4 build-up where this throttle body will ultimately end up being used on.
Having said that, I'm really in no rush to finish the 396, as the current "bolt-on" LT1 in my '92 is running like a champ and I see no reason to pull out a perfectly running motor.
To satisfy my curiosity own though, I decided to install the 58mm throttle body on my stock head/cam LT1 and see what the results are for myself, rather than just going along with internet hearsay.
For the record, this is
NOT the first time I've upgraded a throttle body. I did so on two of my previous vehicles as well, (an '88 L98 Iroc-Z and a '93 LT1 Formula Firebird) but on both those instances, I'd also done other mods in conjunction with the throttle body.Although there was an increase in performance both those times, I can't say for sure how much of the increase came from the larger throttle body and how much came from the other mods that were done at the same time.
This was/is the first time I've installed a larger throttle body on a basically stock LT1. Hence, the reason why I was so curious to see what the results would be - first hand.The mods on my '92 so far, are 1 3/4" long tube headers. Corsa exhaust. Electric water-pump and cut air-lid. The car also has a custom tune from PCMforless. Aside from that, the cam is stock and the heads have never been off the car.
I'm well aware that the factory openings on the LT1 intake are only 52mm and many claim that adding a larger T.B. than 52mm will create a lot of turbulence and actually
HURT performance more than anything.
Again, this was done just to satisfy my own curiosity, so bare with me.
The throttle body you see below is made by TPIS. It's a pretty pricey piece at $450 but the product itself is an absolute work of art.
They're machined out of a solid block of aluminum. They have CNC machined throttle blades. A re-designed throttle linkage cam and come with a billet IAC housing that eliminates the engine coolant passages. Oh and then they're anodized "Plutonium Grey" - which give them a unique look that distinguishes them from other aftermarket throttle bodies.
Like I said, it's definitely a high quality piece.
Now, I'm sure you've all read the usual statements made by people who believe the factory throttle body is all you'll ever need.
The big three arguments against using a larger throttle body are:
- You'll lose all your low-end torque
- Throttle response will go out the window
- The car won't idle properlyWell, now that I've done the "upgrade", - I can honestly say without a doubt,
NONE OF THE ABOVE!I really don't know why anybody would claim those things when it's
OBVIOUSLY not the case. I guess it has more to do with people just repeating what they've heard others say, rather than speaking from first-hand experience.
For starters, the very first thing I noticed, was how much stiffer the gas pedal felt.
It took a bit of getting used to because I now have to press down down on the pedal harder than I did before. It feels as if the throttle blades are either closed all the way, or fully open. It made it kind of difficult to drive off the line normally without chirping the rear tires from a stand still.
Once the car's up and running at speed, again, pushing down on the gas pedal, say, 1/4 ways down, the car lunges forward as if I just hit wide open throttle.
It really transformed the overall "feel" of the car. Once I got the hang of it though, I now actually prefer it.
At wide open throttle, (and take this for what its worth) but in my opinion, the car feels as if it pulls a lot harder up top. I know, I know, without actually putting the car on a dyno, this is only an "opinion" - but like I said, take it for what it's worth - but this car feels as if it's making more power than before at any given RPM.
Coming to a stand still, I literally had to "re-learn" how to launch my car as the first few attempts had me lighting up the tires and hitting the rev limiter like crazy. Like I said, the pedal feel is totally different now and launching "gently" is an exercise in restraint.
Whomever said you lose low-end torque with a larger TB is totally out to lunch on that one.
Idle remains the same as it was before. No choppyness at all. It remains rock-solid.
All in all, I'm definitely happy with the end results. True, that's a lot of money for a throttle body, and although I'd still recommend a set of headers/exhaust/gears before I'd recommend a larger throttle body, I can now honestly say, that a larger T.B. will definitely
NOT hurt performance on a bolt-on LT1, only improve it.
(In case any of you plan to upgrade the stock throttle body, be sure to reset the computer by disconnecting the battery for a minute ow two and then adjust the TPS sensor to .54 volts (reading with the key in the start position) using either a scanner or multimeter, before you take the car out. I just got a dremel tool and"ovaled-out" the openings on the factory TPS sensor and now had enough "front to back" play to manually adjust the TPS.
Anyways, here are some comparison pics.
I'm interested to know of other peoples experience's with larger T.B's.
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LT1*C42010-10-12 07:26:31
LT1*C4
