Throttle Body Spacer.....

oldschool327 · April 4, 2011

So, I know that very few believe or like this mod but here goes some real world testing as I wanted to see for myself to compare to what you all say.

I have ran a Airaid throttle body spacer since about 2K on the clock, I now have just under 60K. Never paid much attention to the negative hype o this board when talking about TB spacers. I understand the con arguement but had some extra time this past few weeks and decided to run some tests with the Cortex and DIC center.

I took the spacer out 2 weeks ago and ran around my normal route to work and various freeway routes. I could visually see a big difference in the DIC center instant and average mileage immediately. After a week I concluded that I was loosing mileage (-2-6 MPG) but had to re verify with close variables.

Ran a specific route back to back on the same day within two hours of each other. 730 am -930 am

Weather was identical both days around 50 degrees and cloudy with little to no wind.

First was a SR country road flat and 5 miles long going 35 mph . Truck would struggle to get into 4 cyl mode and kick in and out very fast average 16.2 MPG. Put the spacer back in and 4 cyl mode could hold almost the whole time average 21.9 MPG.

Next day was a 10 mile stretch down I-5 South bound out of Sacramento at 60 MPH. Yes I was getting passed but never had to touch the cruise control so I didnt mess up the results. Again without spacer the truck NEVER went into 4 cyl mode and averaged 14.7 MPG. With the spacer back in it stayed in 4cyl mode over 50% of the time and averaged 19.1 MPG.

This is all with the Cortex set on 87 Octane performance tune not the Mileage XS tune, GPS verified MPH, 3:73, 4L60E, 33" Nitto Terra's with 5" lift.

I will not claim any HP gains but can verify without a doubt the TB spacer does help with MPG. I know it will be argued and flamed but I now can say with results that they do do something to help out.

dlstewart01 · April 4, 2011

http://www.gm-trucks.com/forums/index.php?showtopic=98170

The computer will keep the same air/fuel ratio with or with out a spacer.

oldschool327 · April 4, 2011

http://www.gm-trucks.com/forums/index.php?showtopic=98170

The computer will keep the same air/fuel ratio with or with out a spacer.

Thanks, Seen that one but doesnt change my results one bit. Whatever is happening it works!

txab · April 4, 2011

I've reviewed lab testing results under controlled conditions. Your figures aren't happening. 6 mpg? Really?

But whatever you like. No flaming here

Superperv23 · April 4, 2011

30% and 35% mpg gains with a an extra inch added to the intake, if gm offered this from the factory they could win the mpg wars for sure, so yeah I am not saying it didnt happen but honestly I would have to see it to believe it

oldschool327 · April 4, 2011

As expected.......Lab results.........Not happening...Guess I am some crazy dumb hillbilly. Yep, Hillbilly = real world results, gotta love us!

I will say my top gain of just over 4 MPG was a direct result of the truck having the ability to stay in 4 Cyl mode with the spacer, nothing else. If it was staying in 4 mode from the get go I would not have that gain but it wont without it.

St Croix River Rat · April 4, 2011

Interesting.

Note that GM does not sell these trucks with 33" Nittos (likely load E range?) with 5" of lift.

Put the stock wheels/tires on and remove the lift and re-do the test and I would bet you will see no difference with or without the TBS. These trucks are right on the threshold in stock form for the AFM to even kick on and be of any use. Adding large tires and a lift basically deems the AFM useless. In your case, the TBS may have done just enough to get your truck back onto the other side of the AFM threshold.

I would love to see the results of a similar test done on a completely stock truck. If there was anythning to gain in MPG by one of these, you can bet your last dollar that GM would have designed them in from the factory. They bent over backwards to gain 1 measly MPG on the XFE trucks.

To get a true test though, you really need to do a much longer, extended mileage test. Try running it each way for 1-2 months (3K+ miles) during the same season with similar driving habits and routes (i.e. commuting). Your ECM may have been re-learning when you removed the TBS, which can affect performance, AFM operation and efficiency.

dlstewart01 · April 4, 2011

The best the AFM can ever do under the best of conditions is tenths MPG improvement. With the cafe requirements that are being introduced by the government, that none of the auto makers can meet, a prudent person would think that they would be all over this. They do have some pretty good engineers and some with PHDs who qualify as scientists. They test millions of miles at their proving grounds each years and they know what works.

The truck is computer controlled. That means it keeps the air/fuel ratio constant at all times. It does not need to relearn to do this. It is an EPA requirement.

To do a meaningful test you must do several tank fulls over the same conditions hand calculating MPG by gallons used divided into miles traveled.

And once again with all the testing and many on dynos, none has ever shown the spacer to add anything to a modern engine. With the exception of the marketing hype by the people selling them.

But hey if it makes you happy go with it. You might even sell this new idea to GM for millions.....

Matt_ · April 4, 2011

There's a guy on the commander forum that also swears his tornado gives him a 3mpg boost. His is "real world testing" too.

Sorry, but I don't believe either. There's too many "controlled" tests that prove otherwise. Also, there is a major lack of technical reasoning on why it would even work! I know lifelong mechanics, guys who drag race on a semi-pro level AND a hand full of good engineers who are also automotive enthusiasts (one of which worked as a designer for performance racing parts)..... not one person can provide a quality/plausible reason for why these products would work. Any "potential" reason is quickly debunked by the logic "well if that's what it does, they really have a crappy intake manifold design".

Just my $.02. Glad you're seeing results though.... go with it!

HawkScot · April 4, 2011

Does the spacer change the sound from the engine at all? Reason is I was thinking back to the 70s when I flipped my air cleaner lid on 1973 chevy pickup with 454 sounded wonderful, but because it sounded wonderful, I liked putting my foot into it more (loved the sound of the 4 barrel opening the back two barrels)...

I was thinking perhaps your driving was different because things sound a bit different with and without the spacer...

mhenshaw · April 4, 2011

Some TB spacers will whistle especially with a CAI.

The stock intake system flows more air then the motor needs. Even some diesels (I think the duramax is one) don't get any beneifit to a CAI because they flow enough air from the factory. So if a turbo diesel doesn't see any gain from a CAI, then I wouldn't see why a 5.3 needs a TBS or CAI.

I have noticed my AFM acts differently with my exhaust, so maybe the OPs truck acts different with his TBS. But I think reducing back pressure would do a lot more than a TBS trying to put a spin on air that has already entered the throttle body.

Matt_ · April 4, 2011

Can anyone think of a logical reason why the AFM would react differently on a truck with a tbs? For the AFM system to change, there has to be a difference somewhere..... what sensor is seeing it and (more importantly) why?

vettelovralexand · April 4, 2011

I can't think of any logical reason why a throttle body spacer should have any positive affect on the combustion performance of the engine when running a consistent air fuel ratio with a proper intake with port injection.

vettelovralexand · April 4, 2011

The stock intake system flows more air then the motor needs. Even some diesels (I think the duramax is one) don't get any beneifit to a CAI because they flow enough air from the factory. So if a turbo diesel doesn't see any gain from a CAI, then I wouldn't see why a 5.3 needs a TBS or CAI.

I hate when people say this. True, an engine can potentially breath through the existing intake up to a certain amount. Eventually you will choke a given size pipe and then the maximum power output will be based on that airflow and the volumetric efficiency of the engine...HOWEVER, the entire intake system is a stack up of pressure deltas. If you can reduce the pressure delta caused by the filter and the intake plumbing, you allow a greater pressure in the manifold which allows for greater deltas in the runners and therefore higher air velocities and more air making it into the cylinder. But, keep in mind that the throttle body itself is typically the main pressure delta in the system, and also is in charge of airflow for most of the day to day operation. This means that any benefit or increase in pressure on the front side can be eliminated by it simply closing down a few more degrees. But, flow should increase for any given throttle position and therefore power should improve for any given throttle position.