Guys using a Q45 throttle body on the stock ECU - Question

adampecush

adampecush

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May 11, 2006
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First off, I don't want any BS about "you should have left it stock, you need a standalone, etc". This is an interim solution that will be rectified by a standalone.

I'm using a Q45 throttle body with a FFIM, on an engine controlled by the stock ECU and an S-AFC2 (for what its worth, I'm working out the bugs from my restoration on stock stuff before I move to a full standalone). I assume there are other guys on a similar setup.

The issue I'm currently having is an extremely touchy throttle, which if I'm not careful, causes a pretty serious jerking in the drivetrain at low speeds. I assume this is a result of more-than-expected air passing the throttle plate per % throttle opening. I've tried closing the idle gap on the TPS (a distance proportional to the cross-sectional area difference), but this hasn't really solved anything. I'm thinking of opening the gap above stock to see if that takes away some sensitivity.

Anybody manage to solve a similar problem?

Adam
 
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figgie

Supramania Contributor
Mar 30, 2005
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adam,


welcome to big bore throttle bodies. That is not only an issue on the Q45 but every single 90mm TB out there save for the OEM 92mm DBW setups from GM and Bosch.

The only option is to live with it :(

The bigger TB has more area when the plate opens so effectively acts like a smaller tb opening MORE. Hell even in Standlalone, you can only compesate so much for physics ;)
 
adampecush

adampecush

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thats kind of what I thought....

Looks like making my own variable-ratio linkage (kind of like the one I had to remove to clear the hood :( ) might be necessary.
 
92nsx

92nsx

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Sep 30, 2005
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I have that setup right now. Q45 on oem TPS and TCCS. And I do NOT like it at all!!! It sucks to drive normal with it or in a parking lot. The throttle is pretty much a on/off switch with it. It is a extremely touchy throttle as you stated.

Go with a smaller TB if you can 70-75mm. I wish I would have. For pics how mine is look on the first page of my build thead ;)
 
Flywest

Flywest

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May 31, 2005
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I've had a 85mm TB on my FFIM for the past 4 years, and I've *always* had an extremely touchy throttle, more especially in 1st gear of course, always thought that having such a huge intake manifold coupled with a huge TB was too much. Smoothing stops and redlights is an art that took a long time to master. I'm really the only one who can drive the car without slamming the entire drivetrain to oblivion ( ACT clutch on top of that ).

I run a standalone, Autronic SM2, the guy who tunes it made some changes around 1000 rpms this spring and it's better, but I fear it will not completely go away until I run some kind of cable that will pull more gently on the TB plate. ( Some kind of spring assembly I would guess. )

I've always lived with it... you just have to adapt, just tell yourself that it flows *alot* better up top when you lay down the throttle ;)
 
gofastgeorge

gofastgeorge

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Jan 24, 2008
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TPS is not the problem.
The problem is that the first millimeter the throttle cable pulls opens up so much more area than the tinny-winnie stock throttle.

I got around it by making an ecentric cam type cable attachment for mine (only a 70mm, but did the same thing).
Basicly, and offset pulley, so that the leverage is greater at closed, and gets less at open.
This slows down initial opening, and pretty much cures the problem.
I did mine buy cutting & chopping some original pieces, and welding them back together.
But I have seen nice billet ones in Japan that were cool.
 
adampecush

adampecush

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gofastgeorge;1379689 said:
TPS is not the problem.
The problem is that the first millimeter the throttle cable pulls opens up so much more area than the tinny-winnie stock throttle.

I got around it by making an ecentric cam type cable attachment for mine (only a 70mm, but did the same thing).
Basicly, and offset pulley, so that the leverage is greater at closed, and gets less at open.
This slows down initial opening, and pretty much cures the problem.
I did mine buy cutting & chopping some original pieces, and welding them back together.
But I have seen nice billet ones in Japan that were cool.
Click to expand...

this was another solution that I was contemplating. It sucks that i had to remove the original eccentric arm assembly to clear my hood...

oh well, fabbing stuff is fun.
 
K

kracin

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Apr 1, 2007
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i run an 80mm x02 throttle body on a custom LARGE short runner intake mani.... but i also run a built a340e tranny. so no problems really.. it can be extremely touchy if you dont know how to press the throttle right, but other than that, i havent had any issues at all with it being so touchy its annoying.

besides, i enjoy have an extremely responsive setup.

i would take a car that jerks when you tap the throttle over a car that has a huge delay when you touch the throttle.
 
adampecush

adampecush

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May 11, 2006
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kracin;1380339 said:
it can be extremely touchy if you dont know how to press the throttle right
Click to expand...

This goes against my whole build philosophy, thats why I have the issue with it. Sure, I've been driving the car for a few days and have subconciously learned to eliminate any throttle-related bucking, but for somebody else, the car is a nightmare to drive at low speeds.

But as figgie said, OEM drivability is not a strong suit of the large throttle body...
 
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figgie

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Mar 30, 2005
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adam,

i know you went this route but there is a reason why the Big 92mm DBW do not have the same comprimises as the old TB.

The old TB are basically a cylinder. GM (and bosch and the rest) learned from this and made the big DBW DB different. Hard to explain so hopefully this pictures shows what I mean.

The top one is most of the typical mechanical tb.

The bottom one are the new DBW that still keep the light throttle control. ;)
 

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adampecush

adampecush

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thats some clever engineering right there.

not that I've done a lot of research on this topic, but are standalone dbw systems available? I know of the motec system, but I'm under the impression it ties into the main ecu.
 
F

figgie

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Mar 30, 2005
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adampecush;1380614 said:
thats some clever engineering right there.

not that I've done a lot of research on this topic, but are standalone dbw systems available? I know of the motec system, but I'm under the impression it ties into the main ecu.
Click to expand...


Never seen a "standalone" DBW system. It usually has to tie into the EMS as DBW REQUIRES two throttle position sensors for safety failback.

TP and TP2.

MoTeC has the capability but it is an "optional" pay.

the Vi-Pec i think has it also but not aware how it works there.

AEM does not. I think Autronic does.
 
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