Big Throat Throttle Body - actual improvement?

[Wade Nelson]

Has anyone here actually installed one of these TWM big throat throttle bodies? What sort of performance gains did you observe?

My general rule of thumb is you can't actually FEEL anything less than about a 10 horsepower gain...

I have serious doubts, however, about a [claimed] 9% increase in rear wheel horsepower. That would require a 20-30 horsepower gain at the flywheel, and I simply don't

a bolt on part bumping the Z's gross horsepower by 30%, unless you COMBINED it with headers, low-flow exhaust, and other bolt-ons.

Here's the PR from the recent ad, which I ASSUME was cut & pasted from the Motorsport website...

"This is a Motorsport Throttle Body for a fuel injected 280Z or 280ZX. It has a 60mm bore that is 10% larger than stock, allowing a 40% increase in air flow. Tests have shown increases in horsepower by as much as 9% at the rear wheels, and cuts in 0-60 times by .5 seconds.

My belief is "If these claims were true every 280Z/ZX in America would have one of these throttle bodies...."

[LeonV]

You'll see no gain, only a more sensitive throttle (increased flow area/throttle angle)...

[EuroDat]

I think their claim is accurate "Tests have shown increases in horsepower by as much as 9% at the rear wheels, and cuts in 0-60 times by .5 seconds.". They just forgot to mention they also installed better injectors, mild cam, good flowing exhaust, larger AFM and sport air cleaner.

Jokes aside. One thing I have learnt about the L-Jetronic system. It doesnt like being modified to gain more horsepower. Just trying to keep these old systems at factory spec is a challenge. If you did change it, you would probably want to change the AFM to a toyota cressida.

Hard to believe you would get 9% at the engine as for the rear wheels?? Thats a big improvement for just a throttle body.

I think I would spend my money on a decent matched set of injectors and getting the wiring up to spec and the thermo temp mod.

Chas

[LeonV]

FWIW: BRAAPs L6 EFI-induction advice and tips. - L-Series - HybridZ

As mentioned, the stock EFI manifold port runners have only 53% the area of the L-28 intake valve!… Even armed with this knowledge, some guys are still fixated on wanting to install larger throttle bodies on their EFI L28 as a first mod. You spend all the money, time, and effort you want on big throat throttle valves, but until those restrictive runners are opened up, exhaust system opened up, optimize the ignition system including advance curve, you will NOT be realizing the engines full potential with any over sized throttle body. ;-)

Braaps recommendations on where to concentrate ones efforts for building more power from their L6 engine in order of priority…

1) Exhaust, Ignition, (quality spark and “tuned” mech curve), Induction, (including getting rid of that AFM!)

2) Cam, (but ONLY after exhaust, ignition, induction upgrades including an aftermarket standalone EFI)

3) Light weight flywheel.

4) Head work.

[EuroDat]

Good point Leon.

I think the Light weight flywheel should be higher on the list. That just my opinion. I lightened mine when I done the transmission and it improved response a lot. Doesnt do anything for horsepower, but that wasnt what I was after.

Chas

[LeonV]

Good point Leon.

I think the Light weight flywheel should be higher on the list. That just my opinion. I lightened mine when I done the transmission and it improved response a lot. Doesnt do anything for horsepower, but that wasnt what I was after.

Chas

I agree Chas, and I'd add gearing to that as well. A 3.36 rear diff makes a 240Z feel rather anemic.

[TomoHawk]

Even with the advice BRAAP posted on HybridZ (and other L28 experts,) I get people insisting that insist I can get BIG increases in "HPs" by putting on a big throttle body, OR a bigger cam, OR headers, even after how you explain how something like the L28 engine is already at maximum performance as it was designed, and the only increase you could get is by perfecting the mechanicals or the FI parts & electronics.

So you just smile and let people offer their "advice..."

[conedodger]

First of all, I have one of these TWM Big Throat TB's sitting on my desk as we type. There is a calculation to determine proper throttle plate size and the Big Throat is almost precisely perfect for a 3.0 Stroker. It would be too big for the 2.8. The second part of my thoughts on this would be that if you're going to change out the throttle body, why not go with DBW? 

When that thing came out, you would almost always get claims like that. 'This thing will increase your horsepower by 10% and make you last longer in bed!'