Big Bore throttle body for MPG?

[cfg83]

Hello -

I just saw this on e-bay :

eBay Motors: Saturn S-Series BIG BORE Throttle Body SC, SL, SW 91-02 (item 300256144389 end time Sep-11-08 18:42:01 PDT)
saturn_big_bore_tb.2.JPG

These throttle bodies are professionally lathe bored to ensure a precise and consistent bore
Not a quick and sloppy dremel job
Each throttle body is taper bored from the throttle plate out to 52mm on the front and back
Gain up to 12hp and Save Gas too!

Do you think this will help for MPG? My semi-edumacated guess says no.

CarloSW2

[hondaguy72]

No way it would save fuel. It gives you less control of high vacuum airflow over a smaller or standard throttle body. The only thing I can think of where that statement might be true is that the TPS values vs airflow would be different than stock causing a potentially dangerous lean condition. Very few aftermarket parts will positively affect FE.

[Daox]

Hondaguy72 is right. There is no way a larger bore throttle body will save fuel. In addition to what he said, the larger bore throttle body will decrease low rpm torque (increase higher rpm torque) which is the exact opposite of what we want.

I don't think you'd have a problem with lean conditions as the O2 sensor will ultimately correct for it.

[cfg83]

hondaguy72 and Daox -

Thanks for the feedback. I didn't think it would work but I didn't know exactly *why* it wouldn't work.

I think a lot of HP mods are just adding the "saves gas!" claim to all their stuff these days.

CarloSW2

[bgd73]

The saturn must have crazy delay timing wise to want a bore that big...variable valves or other gookiness.A dog chasin its own tail is very modern car , and inlines feed that crazy function..
A true stoich from timing at idle on up would not even need 75% of that bore...but that is today and gook injection and gook takin over the world.


Visegrips announced it is moving to china.

[nascarnation]

Also looking at the ad, it appears to me like they are boring the casting but leaving the throttle plate (which is the real airflow restriction) untouched.

FWIW - S Sats definitely don't have variable valve timing (I've owned several - SOHC and DOHC).

[aerohead]

There is a "truth" to what they say,but it's taken completely out of context,as other members intuit,to capitalize on disgruntled motorists attempting gas saving mods.At WOT,the intake tract WOULD be closer to atmospheric pressure,so pumping losses would be reduced a fraction( less than an inch of mercury delta-P).BMW's attempt to remove the throttle body and entire intake(save for the air cleaner) tract,including the camshaft and conventional lifters,is a more visionary approach to reducing losses.---------------- I give the big -bore "the big Spanish Archer" as Burt Munro would say.A big thumbs down!

[Ryland]

ideal air velocity is around 300 feet per second, faster then that and you get restriction problems, slower then that and you loose torque and efficiency, it's similar to running to large of an exhaust pipe, if less restriction was the key then running without any air box and no air intake tubing would be ideal and everyone would have their exhaust exit the side of their car, but that is not how engines work best.

[ATaylorRacing]

From my own experience I can tell you that a slightly bigger TB can give more HP and FE. The TB in the E-bay add would do both, but NO WAY are you going to gain 12 HP! The throttle plate is the same as stock and all they are doing is cleaning up the air flow going into the TB.

On a bone stock 3.0 liter V6 Dodge Shadow/Plymouth Sundance from the early 90s going from the stock 42mm TB to a 52 or 56 one off a 87 mini van with the same, but older motor picks up about .25 seconds in the 1/4 mile and from 1.2-1.8 mpg (1.7 in my case).

On my 98 SOHC Neon I went to a HUGE Indy Cyl Head intake and the FE stayed the same and I lost torque, but gained higher rpm power...no improvement in the 1/4 either (advertised a 25 hp improvement with a bigger TB.....So I bought the AF/X 60 mm TB and picked up a bit over 1/2 sec in the 1/4 and FE became nearly 2 mpg better.

On EVERY car I have owned.....if I was cruising, any air flow improvements into the motor made more FE and power....on MOST a better flowing exhaust did the same thing, but not on the V6...a better flowing exhaust made it have worse power and FE until I did a lot more mods....the stock set up worked the best initially.

What I have found is that with the extra power you can drive up to your speed easier and maintain it with less throttle = better FE.

[TELVM]

Originally Posted by ATaylorRacing

On EVERY car I have owned.....if I was cruising, any air flow improvements into the motor made more FE and power....on MOST a better flowing exhaust did the same thing ...

What I have found is that with the extra power you can drive up to your speed easier and maintain it with less throttle = better FE.

Similar experiences here.

Switching to an oversized TB sometimes brings drivability problems for street & road, however. Unless the OEM TB is clearly undersize for the application (rare), the TB is one of the last things I'd fiddle with in the intake system.


BTW any TB has some potential for improvement. Every bit helps:

[johnmyster]

Air doesn't flow like that.

[Formula413]

Originally Posted by hondaguy72

The only thing I can think of where that statement might be true is that the TPS values vs airflow would be different than stock causing a potentially dangerous lean condition.

I was wondering about that. Lots of people on LS1tech have their TBs ported, shaving off as much excess material as possible. But like you said, that means more air is coming into the intake manifold at any given TPS value. Although it probably is true that the O2 sensors can easily compensate. People who have this done talk of improved throttle response. Well of course, there is more air coming in for any given throttle position.

[jonr]

All this intake airflow stuff pertains to WOT and maximum output. Generally not applicable to moderate output operation and FE.

[Vanner]

I would think a SMALLER bore throttle body would help at moderate throttle positions, given that the air restriction would then "be" at the bore and allow the throttle plate to open up more for a given demand. Nascarnation nailed it: your restriction is at the throttle plate unless the plate is open.

jonr touched on this: for WOT there is no throttle plate and fuel economy should increase with a big bore. Great.

I see this argument as in a similar vane to CAIs, they say if you can reduce intake restrictions the engine doesn't have to "work as hard" (whatever that means) to cruise at some speed. Seems like rubbish, the throttle plate just chokes off whatever progress you make upwind.

Anecdotal evidence is evidence, I know, but there a hundred factors that go into fuel economy. And no one yet has installed a throttle body trying to save money.