throotle body modification or switch - PeachParts Mercedes-Benz Forum

oldsinner111 · #1 01-21-2012, 09:10 AM

Hey all, chew on this info. I have noticed for more performance people installing larger throttle bodies.
Two I can not find where I saw this but this was a throttle body modification on a Dodge Caravan supposed to increase horse power bu 35.
I noticed on my m104 that the throotle never opens wide open.
The same for Dodge Caravan.I saw where they removed throttle plate stops,and allowed throttle full open position.
Can ours be ground off too?

oldsinner111 · #2 01-21-2012, 10:24 AM

Just watch a S500 throttle body also.It does not open fully either.I think I'm on to something.

JayRash · #3 01-21-2012, 12:00 PM

Our throttle bodies do open fully but only when the engine is running. They are half controlled by cable and half by an electric motor. I seriously doubt merc made over 320 hp on the m119 with a not fully open tb. But I'll check on Monday to confirm. With a vid to confirm my findings (I hope )

oldsinner111 · #4 01-21-2012, 03:57 PM

I talked with a tech in Russia he says they don't open horazontaly.All the way.It would be good to get a junkyard TB to experiment on as they are expensive.
One another note using a dremel on the top portion of TB to shape like velocity stack helps alot.With increased air flow.
But again why couldn't you use a 420 TB on a 320?
Oh yes I watch video of 500 they don't either open wide. W140 group on facebook.

JayRash · #5 01-21-2012, 05:05 PM

looking more into this it seems ur correct. what a bummer y wouldnt it open full and how much gain there is, i cant say. got to admit mercs use large tbs for the engines they make.
Still my amg 3.6 has a 70mm tb but wonder if there is more power if the tb does open 100%

yzn · #6 01-21-2012, 06:45 PM

I think you should test it, would be really great if there was increase in performance.

What is the size of the throttle you have?

LandYaghtLover · #7 01-21-2012, 06:47 PM

Oh my. The TB plate position does not matter except at WOT. So any modification will do nothing at normal operating conditions. Just want to clear that up. And cutting a v, does nothing. I dont know why people make this stuff up. Unless its backed up by real dyno numbers and certification nothing else was done (not even a tune-up), then is BS.

And there may be a reason why the TB does not open up all the way. Can the injectors deliver the right amount of fuel for the air coming in? How about exhaust. Your brining in more air, you better better make sure fuel can mix with it right, exhaust can expel it and the TPS can read the position right (if equipped).

The two most common restriction points on a car are, however, the throttle body and the exhaust. The first place any person should start is on better flowing heads and exhaust. Then go from there.

BAD300 · #8 01-22-2012, 01:55 AM

Interesting talk imo

as I asked yesterday on another thread about the M104 tb being 3.25" diameter? The M103 is only 2.75 ish".

I will be chasing 400odd rwhp using after market ECU, direct fire coils & LPI injectors (turbo of course) so, if I can use any size tb why wouldn't I go for bigger?

Would I benefit from a 3.25" on the M103 intake mani (bored out of course if I can???)

Cheers!

duxthe1 · #9 01-22-2012, 02:45 AM

Those inch measurements are off. The 103 TB is 64mm, barely over 2.5 inches. I used a 70mm throttle body blade from a 400E when I made my oversize 103 TB. 70mm is really close to 2.75 inch. Somehow I doubt that the 320 is 20mm larger than the 400. 3.5 inches is just shy of 90mm. I barely got 70mm bolted to the 103 intake. 90mm would be larger than the bolt pattern that mounts it.

FYI, there are pics of my oversize TB in my "view photos" link at the top right of my post.

BAD300 · #10 01-22-2012, 03:32 AM

I just measured both the tb & mani with a steel rule. The tb bottom is 65mm diameter. The manifold port is 66m. Double checked it with a measuring tape too. Sorry for the error but did you by any chance read the thread I saw the M104 3.25" tb mentioned? I don't wanna embarrass the OP on that thread that's all. I thought that was rediculous but am not involved with the M104 engine in any way so I thought I'd mention it to be sure.....

After checking it, yeah you'd definitely only bore the manifold out to 70mm that's for sure. I don't see it being worth the trouble personally. That & the tb.........Thanks for the clear up

EDIT

Here's some comments (slightly edited for our use) I found, concerning turbocharging & larger tb's, that maybe can be cleared up?

a) Turbo installations have the turbo before the throttle body, so the air passing through it is compressed. Thus the size of the throttle body isn't as critical for the turbo. However, concerning a supercharger is trying to suck through the throttle and the air isn't compressed.

b) A smaller bore leads to better throttle control and response (never underestimate) and improved fuel mixing, but perhaps where high HP applications are concerned, this may be a different story?

After further reading, I have found other engines with similar capacity or when cubic inch is considered indeed have smaller tb diameters ie: M103 has a 65mm diameter tb plate, RB30 (3.0L Nissan) has only a 54mm tb plate & the XF Ford (4.0L) has a 64mm tb plate. As Jay says, Merc tb's are big for their motor cc so, perhaps they don't need to open fully?

@ JayRash, so, which is it

Quote:

Originally Posted by JayRash

Our throttle bodies do open fully but only when the engine is running. They are half controlled by cable and half by an electric motor.

Quote:

Originally Posted by JayRash

looking more into this it seems ur correct. what a bummer y wouldnt it open full........

Reason I ask is since I am not using the M103 ECU or any motor, should I be tossing the original tb & go for a 64-65mm tb that does open fully?

BAD300 · #11 01-22-2012, 08:10 AM

oldsinner like you I'm not sure about this just wondering really myself

oldsinner111 · #12 01-22-2012, 08:47 AM

Looks like to me 15% to 19% throttle opening left.

BAD300 · #13 01-23-2012, 03:11 AM

Just to clear up some things concerning the M103 tb. I can see where perhaps the misunderstanding is.

I have mine off so I have measured it all over.

oldsinner111, dunno about the M104 but the M103 tb is tapered quite a bit so it is actually shaped like a velocity stack! Also, butterfly opens all the way meaning, 90 degrees to the body plate! It cannot open anymore else it would go back the other way.

Here are the exact measurements:

TB bottom plate diameter = 65mmID
TB butterfly/innerID diameter = 64mmID
TB top plate diameter = 76mmID & 79mmOD.....perhaps this is where another post was seeing it from?

RBYCC · #14 01-23-2012, 11:10 AM

Why not just a basic throttle body spacer ?
In essence it increases the "gulp" or amount of air that the throttle body flows to the intake.
The TB on an injected car functions no differently then the throttle assembly in a carb.
Sometimes going back to basic "hot road" techniques does more then trying to modify parts that aren't easily modified.

Below you'll see a 1" aluminum TB spacer that I had custom machined for a modified LS2 in my 06 C6.. (which I eventually traded for a 1971 W113 roadster.)

MAG58 · #15 01-23-2012, 12:08 PM

Quote:

Originally Posted by RBYCC

Why not just a basic throttle body spacer ?
In essence it increases the "gulp" or amount of air that the throttle body flows to the intake.

lolwut? I'm in for an explanation of how increasing the plentum volume post throttle valve increases air quantity.

Quote:

Originally Posted by RBYCC

The TB on an injected car functions no differently then the throttle assembly in a carb.

Except in a carb there's fuel flowing past the throttle valve. That's kind of a big difference.