TBI Spacer Dyno Numbers!!!!

[some1else]

OK everyone-
Now that I've suckered you in....

I am hopeful that this will become the definitive post for TBI spacers.

This post pertains to the older (95 and earlier) throttle body injected trucks only. No vortech, MPFI SFI etc. Only engines using throttle body injection.

I am looking for independent proof that any (type, brand etc.) TBI spacer provides an increase in power. So to any end-user (not sponsor or manufacturer): I am talking dyno results here.

So many people argue whether these things work.
Lets find out once and for all!!

If you've got numbers post them here.

If you have a spacer and you are convinced it works, do us all a favor and make back to back drag strip runs or dyno pulls with and without the spacer. If you're g-teching it, average 5 or 6 runs with, and 5 or 6 runs without the spacer.

Thanks for any posts. (with numbers )

[vhato]

I wish I had the numbers. I had a '95 TBI back in '95 and I added the Turbo City TBI Spacer and Injector Spacer. I gained NO PEAK HP and NO PEAK TORQUE. Would I buy them again. YES!!!

When examing the results I realized I gained a substantial amount of power in the MID Range where I needed it since I drive on the hwy. The '95 TBI had 300ft lbs torque. So I knew I could tow anything I wanted. Adding thoses devices made pulling my boat NOTICEABLY easier on the Hwy since the sweet spot is in the Mid Range. I did lose some SOTP Throttle Response though, but worth it to me.

[Rich Mlnarik]

Maybe I can help.

I have dyno numbers from 1992 when I first moved to CA where there was a dyno at Turbo City. I ran my truck many times at the track in Scribner, NE in the early 90’s. In 1991 a friend of mine that owned a tool and dye shop made two spacers for me, a ½ inch and a 1 inch.

I went to the track and ran with both spacers, with the truck in drive and shifting at 4500 rpm, my times were the same in the 15.50s. Two weeks later I went back, the weather was the same, my records show low 70s temps the end of May. I ran two runs, still 15.50s. Went back to the pits and installed another governor that I had lightened the weights on to shift at 5500 rpm. Next run with 1 inch spacer I ran a 15.37. The rest of the day I was running in the 15.30s. My combination back then was stock motor, stock cam with 1.6 rockers, Edlebrock headers, stock cat, dynomax super turbo muffler, TBI injector spacer (2 gaskets), hypertech chip, 410 posi rear end, MT sportsman pro tires, and the governor.

Moved to CA in Sept 91, went to the track at Carlsbad Raceway to run the truck, ran 15.20s (sea level). From that point everything changed. I have dyno'd with different cams and combinations over the years.

Here are my dyno runs from 1992. I won’t list the speed or torque. I am sure dynos have changed from 92. I will just list the hp.

Turbo City Dec 17,1992 Start time 14.29
HP No Spacer
4000 rpm 155.3
155.7
4500 rpm 164.6
168.2
5000 rpm 153.4
153.1
5500 rpm 153.5
152.0
HP 1 inch spacer
4000 rpm 148.2
148.7
149.0
4500 rpm 159.6
159.4
160.1
5000 rpm 172.1
171.8
171.4
5500 rpm 177.1
176.9
176.5

This is all I can add! I still run the 1 inch spacer today. I have bracket raced this truck for 12 years. I have many ET slips from many tracks. I last raced at Carlsbad Raceway Nov. 2003 at the Outlaw Brackets in street class, runner up at 13.69 @ 97.28.

Remember these are just my records over the years, with my combination '88 350, TBI automatic, ½ ton short wide 2X4.

[some1else]

Rich-

Thanks tons for the informative numbers. Here is an example of some top-end gain, with some low-end loss. Too bad our trucks shift at 4500.

[Silverback]

Well, I just got linked here so it's a little late but I figured I'd reply.

I don't have dyno numbers, and it's not a truck, but I have tinkered with this on an f-body with an L03 (305 TBI used in the late 80's, early 90's, same one that is on the trucks). I custom made a spacer out of 1" hardwood (soaked in fuel proof dope) and a 5/16" thick injector tower spacer and actually saw .4 at the track, that's a big improvement. I suspect that part of it was more airlow, and part of it was getting the injectors up higher resulting in better fuel distribution.

[retorq]

This spacer you are running, is it the two hole or a single big hole (or knife edged divider)?? I'm familiar with spacers on carbs and there are two types, open and 4 hole. The 4 hole just increases the pleneum volume, helping with higher end HP. The open will allow a std dual plane to pull air from both sides of the carb, effectively increasing your air / fuel flow. If what they say about the TBI setup on my 95 is true, I should see a performance boost using a knife edged or open spacer, I don't spend much time above 3000 rpms so the 2 hole spacer / pleneum increase really won't help me much. Thoughts??

[Silverback]

I my case, 2 holes cut to exactly match the openings on both sides of it

[derek_silverado]

I suppose I'll put my .02 in here.

From what I theorize, the spacers serve to lengthen the intake runner length and also to allow slightly more opportunity for fuel atomization. Engines are designed a certain and certain things are designed to match other components. For example, the intake manifold is designed to work with the valvetrain to place the torque curve in the desired location. If I am thinking correctly, lengthening the intake runners (which is kind of what a spacer does) has the potential (depending on the design of other engine components of course) to place the torque curve lower in the RPM range. This however, may/will sacrifice higher end power because horsepower is a product of torque and rpm. If peak horsepower was increased by a spacer I would assume that it was due to more effective atomization. If everything else was being done effectively (ie: exhaust clearing the combustion chamber, correct timing, adequate air delivery) that the throttle body spacer would be useless. Therefore, get a throttle body spacer only if you are looking to shift your powerband slightly lower, as the intake runner length is already designed to work most effectivly with the valve timing and other important processes.

I'm no automotive engineer, so some one please tell me if I am wrong in anyway.... I don't think I am, but it's possible.

[Silverback]

You're partially right and partially wrong… yea, longer runners will change what rpm the intake is tuned for, and assuming that we're talking about the same harmonic a longer runner will tune for a lower rpm.

Adding a plenum spacer does not lengthen the effective runner length. It does increase plenum volume and helps top end rather then low end (it will actually hurt responsiveness slightly, but so slightly that I'd bet that no one would actually feel it). I think that most of the change is due to getting the injectors up higher helping fuel distribution and airflow…

[derek_silverado]

Hmmm, interesting. Looks like I was a good bit wrong.

Thanks for the clarification.