Topic: Throttle body question

[frosty]

Now that the wheel rubbing issue is solved I have a 4.0 throttlebody off of a 2000 cherokee.  What would be the best combo of TB spacers to install it with to get the maxinum power and what kind of power increases should I expect.  i do have a K&n airfilter.  Oh by the way this site is the best thing on the internet.

[jcsanders79]

I have a throttlebody spacer that I bought on www.ebay.com for about $30. It mounted up great with my new throttlebody.  Thats a lot cheaper than the brand names.  I also put a cold air intake on.  I would suggest a header and new exhaust.   It seems that I have to much air going in and not enough out (waiting for UPS to bring me a header)  but even then I did see an improvement in performance.

[frosty]

Should I go with a 4.0 spacer or a 2.5 and how high?

[Jesse-James]

Measure the bore on the throttle body and get one to match, mine is a 62mm off a 4.0 HO. Jeffy can probably tell you without measuring though. Hieght should be 1 inch.

[chrisfranklin]

why stop at one? Two spacers'll fit.  

[damon54]

That is a question that I have too.  I am putting a brand new 4.0 throttlebody on but I have a spacer that is set up for the 2.5 tb.  Would it benefit to change to the 4.0 spacer too?

[SMC4WD]

As far as I know...  The Throttle Body spacers are the same for the 4.0L & the 2.5L...  

I could be wrong, I'll have to look at AirRaid's website.

EDITED TO SAY: I'm wrong...  they are different.  Sorry :(
http://www.airaid.com/spacers.asp


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[Jeffy]

The stock TB for a 2.5L is something like 46-8mm.  The 4.0L is 54mm.  If you have a TBS already I'd jsut use it.  If it's one off ebay, I believe those are cut to one size, 4.0L and sold as both.  Poweraid's are cut to two different sizes but you could hone one out on a drillpress fairly easily.

Why you only use one?  Because it has to do with the length of the run between the throttle valves and the intake valves.  What you're doing is fine tuning the pulse/ pressure wave created and trying to get the wave so it hits the intake valves right as the valves open, causing a forced induction effect.  You can do this with the exhaust also. Althought you want the exhaust pulse to arrive at the exhaust valves before they open.  This will cause vacuum effect as the pulse heads back to the exhaust tip.  That's the simple answer.

[damon54]

I went ahead with the 2.5 air raid with the 4.0 throttle body because I don't have the patience to send the spacer back.  I did encounter a lot of sludge and buildup in the intake below the tb.  Is this something I should be worried about?

[chrisfranklin]

Truth be told, I actually experimented with two 4.0 PowerAid spacers in 2004, just for kicks when I was staying in Whittier, Ca.  Was able to pull it off -- one space on top of the other -- because the extended bolts you get on one spacer kit will give you just enough purchase with the intake to accomodate a second spacer.  However, you only have a few threads holding the whole 2 spacer and TB apparatus in place, so this was a precarious execution, at best.

However, Jeep didn't run any better. Actually seemed to run worse, even after a couple of weeks.  Because of this, I went back to one spacer and sent the other back.  Never really had an idea why it wouldn't work better than one alone, until now.

Don't want to shine Jeffy's trumpet too much on this one, but it sounds like he has a point.