Topic: anyone running or know about 62mm throttle body

[Jhcujo]

The question that I have is are they bored out to 62 all of the way through or just on the bottom side of the butterfly valve?  I have a extra TB and where I work there is a machine shop that I could get to do the work for cheap. I think that just the underside is bored out but wanted to check and does anyone think that 62 all the way through even the butterfly would be a problem.

Thanks Joe

[Jeffy]

I don't recommend going with a 62mm bore.  You can run into idling problems unless you've done enough with the intake, exhaust and internal work to warrant a a 62mm.  Also keep in mind, by boring out the whole TB, you will need to make new throttle plates.

[chrisfranklin]

I gotta admit, I bought a 62mm TB for about 100 bucks off a certain auction site.  It seemed to cause the Jeep to idle at 1500 rpm for a week, but ultimately the ECU seemed to adjust for it and idle returned to about 800-900 or so.  

Actually, has been ok, especially  for the money; there was a core charge, though, which was only refunded upon shipping the core to the seller.   TB appeared to involve a fairly class manufacturing job.

[Jeffy]

I gotta admit, I bought a 62mm TB for about 100 bucks off a certain auction site.  It seemed to cause the Jeep to idle at 1500 rpm for a week, but ultimately the ECU seemed to adjust for it and idle returned to about 800-900 or so.  

Actually, has been ok, especially  for the money; there was a core charge, though, which was only refunded upon shipping the core to the seller.   TB appeared to involve a fairly class manufacturing job.

That's a bit different.  The problem with running a TB that's too big is that too much air gets into the engine and the PCM can not compensate.  Lower speeds, it might not be a problem but when you start getting the RPM's higher and get closer to WOT, you'll probably run lean.  The other problem that another guy is seeing is a slight missfire.

[chrisfranklin]

Before install, I measured the diameter on bore of the TB and it was definitely 62mm.  I was wondering about lean running conditions for other emissions-related reasons, but if anything, the TB seems to have improved performance at WOT.  I get on an uphill on-ramp for the 101S and the 4 revs way more strongly well-through 4000rpm.  And, the engine is already warmed-up.

I don't note any misfires.  The 62 TB is no supercharger, but it is a modest improvement for higher RPM running.   Lower RPM I do seem to be able to cruise around more in 5th gear on low mph city streets, so maybe low-end is improved some.  

Probably the only other engine mod I am considering is an adjustable MAP sensor (in case there is a lean condition resulting from other intake mods, etc; but performance currently seems good and CARB is a bitch  :) .   No supercharger, turbo or even headers (nervous about engine mileage and don't really need any more high-end power vs. the costs involved)

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Other than repairs, a Locker(s) is/are about the only thing on my buy agenda and I'll probably chince and go with a rear Aussie or No-Slip based on decent reviews of these quieter, modern alloy lunchbox jobs.  Using the D35 rear on 29" tires (and no plans for a tire diameter increase), I plan to roll the dice that the D35 can take moderate 4x4 wheeling where a wheel might leave the ground once in a while; axle will likely still break, but Jeez man, 29" was the top size from the factory back in the day; we are not exactly talking 35s, 33s or even 31s or massive, modded 4.0 low-range torque!  :evil:   (I feel an, "I told you so", coming a long regarding an upcoming D35 snap on 29s, though)

You know you will never see this rig anywhere near "The Hammers" and its like (and I am just looking to have an easier time on the "Miller Jeep Trail" and maybe some of the Big Bear trails)  A second rig may be a different story, though, at least with regards to running hardcore trails  and using corresponding big tires/axles

[chrisfranklin]

Also, my experience with the 62mm TB may not be the same as everybody's on the site and frankly, I don't have a real good basis for comparison between before and after other than SOP feel.  So buyer beware.  

Anybody know by chance what the voltage is on a stock '94 YJ4 coil?  The aftermarket Accel coil I use says max is 42k Volts.  Stock is like 30k, right?

[Jhcujo]

I thank you all for the input. Since I have a complete extra set up including intake manifold and throttle body I think that I will give it a shot. If nothing else I can always go back to stock. The manifold is already bored out to 62mm. Plus I am planning to put on the adjustable MAP sensor just to try to prevent running lean.The one question that I still have is. Do they bore the whole thing or just the underside of the butterfly?

[Jeffy]

I thank you all for the input. Since I have a complete extra set up including intake manifold and throttle body I think that I will give it a shot. If nothing else I can always go back to stock. The manifold is already bored out to 62mm. Plus I am planning to put on the adjustable MAP sensor just to try to prevent running lean.The one question that I still have is. Do they bore the whole thing or just the underside of the butterfly?

You should be ok if you match the bore at the throttle plate, removing the taper.  Anything more and you'll have to replace the throttle plates. And thats when you may run into other problems.

[chrisfranklin]

The underside on my 62mm TB definitely got bored out big.  Before I installed, I compared the old stock 2.5 TB with the 62mm TB and it looks like the top-side of the 62 is definitely larger in diameter; mine was equipped with a replacement TB plate that was thinner than stock, was "brass" and appeared to be custom for this modification, also.  

In sum, mine appeared to be a 4.0L TB that was bored out top to bottom and then fitted with a different "plate" to accomodate the larger bore.  I don't think I could have built this TB economically if I had tried to DIY or use a machinist, but that's just me.

[MA2LA]

I was loking at a spare intake and a couple 4.0 TBs today and the stock intake opening is the same as the opening on a stock 4.0tb so goin anybigger than that with out moding the intake is useless. I am considering removing the taper like alot of guys do and match the intake to that witch would be 60mm all the way through.

[littleredbeater]

I put in a 62mm throttle body and helix spacer that is 62mm and it was aa nice gain so far. But based on advice here I don't go WOT much, Until I get an adjustable map installed.

Are you saying the intake manifold is only 60mm? I should have meansured it.

I've had no issues with idle or anything else yet. Those security torx screws suck balls though.

[MA2LA]

The stock intake is actualy less than 60, the stock 4.0 tb is tapered down to 58 i belive an its a direct match for the intake. I just put a 2 on my dads ZJ to see how it would do and its pretty good but for a motor with little other mods i think its to much, I deffinatly need to do the adjustable map. I tryied one of those python computer add ons and it did nothing but screw it up worse.

[chrisfranklin]

Crazy thing is that I may need an Adjustable MAP just to get in good graces with CARB.  I think the intake mods and 62mm TB I use may  cause a slightly lean running condtion which effectively causes my NOX reading on the Smog machine to skyrocket (often caused by lean running condtions; all other parts usually causing the problem have checked out or been replaced).  

So, believe it or not, I may need "more fuel" to get my Jeep smogged properly and my NOX levels normalized.  Or, I have to pull the intake and TB and swap for stock during emissions runs (have to do the intake pull anyway, for tests).

I may just drive to Turbo City, have those guys install a MAP Adjuster and dial the fuel curve until running is optmized and all is cool with SMOG.