Bored Throttle Body Question.

[Hypoid]

I'll collect some data this coming week.

Starting point:
1990 XJ, 4.0, auto, 4wd.
Induction is stock EXCEPT for the 19-lb Ford/Bosch injectors.
Exhaust is stock to the muffler. Muffler and tailpipe, bring the drone at cruise.

Feel free to toss around theories about flow dynamics, volumetric efficiency, and engine dynamics. I am up to having my brain stretched a little more.

 

[Fred]

Being older and deafer helps with the drone. I'd be curious to see if just a bored TB made much difference on your setup. I'm doubtful, but starting with a 20% loss due to altitude, it may make a difference. I wouldn't classify better injectors as a difference in induction, induction is airflow, and has nothing to do with fuel provision.

 

[Redsnake]

I'd wait....

Looks like Jeff had one in stock and we worked out the sale. Should have a 63mm TB on the way soon. Hopefully I'll be $$ well spent to tie in with my Borla exhaust and Open Cold Air Intake.

 

[GregGA]

Looks like Jeff had one in stock and we worked out the sale. Should have a 63mm TB on the way soon. Hopefully I'll be $$ well spent to tie in with my Borla exhaust and Open Cold Air Intake.

Great! You will enjoy it.

 

[Redsnake]

Got the new 63mm TB f/ Jeff on Saturday and installed it. Easy-peasy install and the results are nice. Obviously it could be a placebo effect but the initial throttle response is much snappier and I haven't had any negatives yet. No whistling, no strange idle, all is well.

Here's a pic of the OE (left) vs. 63mm (right) TB. You can see the difference based on the gasket.

 

[cruiser54]

Great. You'll enjoy it.

 

[GregGA]

I really notice the improvement at around 3000rpm. Next time you go on the freeway, get it up to 3k in third, and stomp on it. Let us know what you think. Thanks for the picture!

 

[Fred]

I drove my 90 from COS to Loveland and back, about 250 miles. This includes going over a 7300 foot pass. I forgot to pull the ave speed off of the GPS, but it had to be over 65 mph. Most of the way the speed limit is 75 mph, and with a little rowing of the gears, I kept that speed, generally at 3k to 4k rpm going uphill. I have 33" MTR's and 4.11 gears for those that don't know. I easily hit 80 mph on the flats. I got 15 mpg, the best mileage my worn out 4.0 has managed in years. I notice the improvement from just over idle to ~4500rpm, but, yah, 3000 rpm in 3rd is fun.

 

[Hypoid]

Nice! maybe some of the more knowledgeable members can tell us where the torque starts to take off, and peak, with the factory cam.

Before the TB, it made no difference, with other intake mods

I forgot to ask, what are these intake mods you speak of?

 

[Dr. Dyno]

Nice! maybe some of the more knowledgeable members can tell us where the torque starts to take off, and peak, with the factory cam.

If you're referring to the '91-'95 cam, it peaks at 3500-4000rpm in a 4.0 but makes decent power from ~800-4800rpm. The '96+ cam peaks about 500rpm earlier and starts to drop off from ~4600rpm.

 

[Hypoid]

If you're referring to the '91-'95 cam, it peaks at 3500-4000rpm in a 4.0 but makes decent power from ~800-4800rpm. The '96+ cam peaks about 500rpm earlier and starts to drop off from ~4600rpm.

And the RENIX cams?

 

[Johnnie Walker]

And the RENIX cams?

IIRC, Renix peak TQ is around 2500rpm

 

[Fred]

Nice! maybe some of the more knowledgeable members can tell us where the torque starts to take off, and peak, with the factory cam.

I forgot to ask, what are these intake mods you speak of?

3" fancy air filter(I forget the name, it was the company that first added the pleats to the end of the filter, unlike the KN of the day. Definitely has more surface for airflow than the stock filter. Made my own adapter out of 3" copper pipe. I had smoothed the transitions in the stock throttle body, and also on the bored T-body. I have a cold air dam between the exhaust and the intake. I used to measure the temp at the intake, and while it was cooler than under the hood, it does not maintain ambient temperature under idle or slow speed conditions. That's it. Nothing real significant. With the bored t-body, intake noise becomes very impressive around 4000 rpm. I likey.

I wonder which would have more effect, valve lift, or a more aggressive cam.

 

[streetxj]

The renix cam is the same cam used in the 91'-95' HO. The difference is that it is more advanced timing-wise compared to the 1st gen HO. That's why it's peak torque is much lower than the 91'-95' HO.

 

[cruiser54]

The renix cam is the same cam used in the 91'-95' HO. The difference is that it is more advanced timing-wise compared to the 1st gen HO. That's why it's peak torque is much lower than the 91'-95' HO.

You're absolutely sure about that?

The cam timing.

Yes, the cams are the same.

 

[Dr. Dyno]

You're absolutely sure about that?

The cam timing.

Yes, the cams are the same.

The info. I've found suggests that the cam was installed in the Renix 4.0 with a 110.5* ICA and in the early HO with a 120* ICA.

 

[cruiser54]

The info. I've found suggests that the cam was installed in the Renix 4.0 with a 110.5* ICA and in the early HO with a 120* ICA.

Interesting. Change in cam or crank gear then I'm guessing. Retarding the cam timing has the effect of an EGR valve anyway.