What effect would larger throttle body have on 99 stock 4.0L

[charley3]

I'm pretty sure a large throttle body helps when intake and exhaust are ported, but would it help me with stock (unported) intake and exhaust? Would a larger throttle body cause driveability problems on a stock 1999 4L engine?

I'm considering a 62mm throttle body. Also curious about 65mm throttle body.

I have high flow cone air filter, but that's my only engine "mod" so far.

[IH 392]

I have a 62mm TB on my '97 with the '99+ intake, K&N and cat back with a gutted converter, works GREAT! NO driveability issues at all!

[SilverXJ]

I had the larger throttle body on a stock 4.0L and it helped throttle response immensely. I would go with strokedjeep.com. Right price and his don't whistle.

[5-90]

I'm pretty sure a large throttle body helps when intake and exhaust are ported, but would it help me with stock (unported) intake and exhaust? Would a larger throttle body cause driveability problems on a stock 1999 4L engine?

I'm considering a 62mm throttle body. Also curious about 65mm throttle body.

I have high flow cone air filter, but that's my only engine "mod" so far.

It will improve part-throttle response - a small angle change in the throttle valve will have a larger effect on flow restriction.

A bored throttle body is NOT a power adder on its own - and is generally not strictly necessary to performance, since even an OEM throttle body will support up to a moderate stroker without any trouble.

If you REALLY one one, save yourself a few bucks and pull a throttle body off of a V8 Mustang - should bolt right up (V8-302 would be about what you're thinking, I think the bore for the V8-283 is a bit smaller, but I won't swear to it. Both should fit the mounting studs, but you can verify that with a quick measurement.)

[charley3]

I had the larger throttle body on a stock 4.0L and it helped throttle response immensely. I would go with strokedjeep.com. Right price and his don't whistle.

I never heard of any brand of larger TB whistling.

It's the TB spacers that I've heard of whistling during acceleration. I could tolerate a little whistle during acceleration, but not during cruising. I wonder if spacer whistles during cruising?

[charley3]

Would a larger throttle body (like 62mm) help if I had high flow air cleaner, intake and exhaust ported, JBA header, higher flow cat, and cat back exhaust?

I want to increase torque and HP at mid rpm range (2500 to 4000 rpm) without losing any torque or HP at lower rpm range (idle to 2500 rpm). Would the above setup accomplish that?

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P.S - I live between mountains in Cascade Mountain Range. I need more torque and HP for the mountain passes on highway. Specifically need more poop from 2500 to 4000 rpm where I drive a lot and is gutless. My lower rpm performance from idle to 2500 rpm is great. Lots of lowend torque from my stock 4.0L, which I use a lot, especially off road. I want to retain my lowend while improving torque and HP in mid rpm range.

[SilverXJ]

[quote="charley3"I never heard of any brand of larger TB whistling.[/quote] I've had both. The spacer didn't much, but the throttle body did. Usually during a gentle acceleration. If WOT or cruising it won't whistle. Heck, if it whistled during cruising it would have been ripped out hours after I put it in.

Would a larger throttle body (like 62mm) help if I had high flow air cleaner, intake and exhaust ported, JBA header, higher flow cat, and cat back exhaust

Yes it would. 5-90 is the first person I heard that believes the stock throttle body is large enough for any stroker.

[shawnxj]

talk to that flyingryan dude about a tune since your profile says you have a 98. it won't cure all your ails but it should help some

[charley3]

talk to that flyingryan dude about a tune since your profile says you have a 98. it won't cure all your ails but it should help some

My profile was wrong. Sorry. I corrected it. My XJ is an early 99 with cap and roter.

Does your tune advice still apply? If so, please elaborate.

[shawnxj]

yes the computer can be tuned to make more power and better mileage. talk to flyingryan....think that's his name

[5-90]

[quote="charley3"I never heard of any brand of larger TB whistling.

I've had both. The spacer didn't much, but the throttle body did. Usually during a gentle acceleration. If WOT or cruising it won't whistle. Heck, if it whistled during cruising it would have been ripped out hours after I put it in.

Would a larger throttle body (like 62mm) help if I had high flow air cleaner, intake and exhaust ported, JBA header, higher flow cat, and cat back exhaust

Yes it would. 5-90 is the first person I heard that believes the stock throttle body is large enough for any stroker.[/quote]

I'll have to dig up the flow numbers & check - but the ChryCo-spec TB, as I recall, flowed enough for up to about 4.7-4.8L of stroker (assuming peak VE of 88%, which is a bit high for the head design) without any trouble up through 5,500rpm. I think.

But, a bored throttle body is not RPT not a power adder in its own right! Most of the "power adding" is measured using the Mk1 Mod0 "Butt Dyno," mistaking part-throttle response for increased output. (The improved part-throttle response is a simple matter of geometry.)

But, reports from the field have indicated useful output & response with at least a 4.5L stroker, so I'll go with that until presented with data to the contrary.

Anyone want to give me flow data for OEM and aftermarket throttle bodies?

[SilverXJ]

I personally like to go off testing than some numbers.

[5-90]

I personally like to go off testing than some numbers.

First theory, then practise. That's how it works...

[SilverXJ]

No, in this case testing is better than going on a hearsay theory. Which is hard to do if you only have access to numbers, but flaunt them if you like.

This isn't an exact science and plugging in numbers usually doesn't get you very far.

[shawnxj]

you 2 going to start your pissing match yet again?