Looking for some first hand experience here, anyone here mount a 70mm TB on a 4.7 with a hogged out TB spacer? (ditch the spiral cr@p stuff and make the bore smooth to match 70mm, basically to extend the TB out an inch and increase the intake manifold volume).

Wanting to build more low end torque on this motor and intake manifold research points me to 2 things, 1 being a longer entry into the manifold past the throttle body. Interested in improving power from 1k-3k rpms, where my engine lives... (already have a whole list of todo items ahead of any TB spacer work).

Ultimate goal, 1st getting mpg's on the 2002 QC 4wd 4.7 3.55 geared project I have up to 20 mpg to start (currently have gone from 14.3 up to 17.8).

I am aware of the sentiment on the TB spacers in general and how they "dont work". There are the end users that did claim a change to low/mid power in throttle response, I would guess it is something like 40% of the end users. Interestingly though, there were a higher number of positive feed back posts in one crowd of motor heads... I forget what car/engine that was though.

 

I’ve always heard spacers are useless on a port injected engine.

 

Mr. Keaton is correct. TB Spacer does absolutely nothing on a port injected motor. Nada. Zilch. You may actually LOSE power.

 

yeah i read that a lot, but never found anyone who bored out the spacer to extend the tb out away from the intake... and have not seen anyone with a larger tb with one.

 

Remember, your intake is actually tuned..... changing plenum volume will change the parameters, and likely not do nice things for the tune.

The whole idea behind throttle body spacers in the first place, was to introduce more turbulence to the air stream, to help keep the fuel droplets in suspension, and it kinda worked, but, as there IS no fuel in the air stream on a port injected motor, more turbulence doesn't help performance, it hurts it. And as said above, changing the size of the plenum, may do you more harm than good.

You can try it, but, don't expect much in the way of results.

 

a lot of that comes from dyno plots with the motor at wot, it is harder to quantify part throttle performance, i believe it can he done on the dyno but would have to have a test plan to execute to find out what, if anything it does..

or.... setup a test fixture to analyze its effect on flow

 

yeah that is indeed true but someone figured out the helix (?) design did something and some companies latched on to it. if i were to set up a fixture i i wou generate a fixed airflow at the source
and measure the flow well after the tb before then after the tbs install. the answer is in the data.

how that flow would affect the engine performance tho probably depends on the intake mani setup. one forum i was reading the guys who popped them in, every one of them claimed to feel bottom end to mid range power bump.

if i bring back the fan test chamber, i may pick a cheap one up and play with it

 

Spacers aren't TOTALLY useless.....drill it, tap it, insert nitrous nozzles.

 

what was your experience with it?

 

That it's easier to just get the nitrous plate already setup.