58mm Throttlebody
Thread Starter
Navigator
Joined: Jan 2008
Posts: 9
Likes: 0
58mm Throttlebody
Hey Folks,
Just wondering if anyone has experienced a flat spot when replacing the factory throttle body with a 58mm unit. It seems as though I now have this sort of flat spot around 1800-2000rpm at mild throttle. Below that and above that it is a real champion. Any help would be nice.
Just wondering if anyone has experienced a flat spot when replacing the factory throttle body with a 58mm unit. It seems as though I now have this sort of flat spot around 1800-2000rpm at mild throttle. Below that and above that it is a real champion. Any help would be nice.
Drifting
Joined: Nov 2005
Posts: 1,324
Likes: 5
From: Charlotte NC
I have not replaced my stock tb, but can I ask why you replaced yours with a 58mm? Did you do other mods as well?
Reason I ask is that a 58mm tb is pulling in a helluva lot more air and I'd think it would cause problems on an un-modded engine. I'd also think you'ld want a pcm tune as well.
Reason I ask is that a 58mm tb is pulling in a helluva lot more air and I'd think it would cause problems on an un-modded engine. I'd also think you'ld want a pcm tune as well.
Pro
Joined: Mar 2004
Posts: 553
Likes: 6
From: Northern VA
I put a 58mm TB on my 383 and immediately experienced an idle lope. I had a pcm tune done to match the new motor and the lope dissappeared as soon as I put the original 52mm tb back on.
It was a waste of money in my opinion and un needed.
CFI-EFI it's good to see you posting again.
It was a waste of money in my opinion and un needed.
CFI-EFI it's good to see you posting again.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
As I have previously posted , I did back to back testing 48mm v 58mm (350 ,intake mods , SLP's, ZZ4 cam,A4 , 3.07's)
30 runs on same day;
No difference in ET /speed , no difference in 60ft , no WOT lag / flat spot ,no drivability problems.
Obviously not a worthwhile bang for buck investment but not the horror story some claim ( loss of bottom end , etc)
Melting Slicks
Joined: Jun 2002
Posts: 2,705
Likes: 30
From: Chesapeake Beach Maryland
2015 C5 of Year Finalist
My 58mm seems to working and running fine. I'd like to see how it would do on a smaller one but I'm too lazy to go changing things right now. I'm still running a good PCMforLess tune right now, but plan on taking for a dyno tune in the spring. We will see then what shakes out.
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Thread Starter
Navigator
Joined: Jan 2008
Posts: 9
Likes: 0
answer
I have no mods yet. I was informed that this TB would be the way to go as it is not a "re-made" piece, that it's a fully machined unit and as I start the mods, it would be a great addition. When I inquired as to any difficulty on a stock motor - I was informed this shouldn't be a problem for now. It is not a huge problem if it is going to go away as mods get done, but if not, this would really suck.
The mods planned for next season are ported heads, cam, LT headers/hi flow cat/and exhaust. I will also be doing some sort of air intake mod and computer tuning.
The mods planned for next season are ported heads, cam, LT headers/hi flow cat/and exhaust. I will also be doing some sort of air intake mod and computer tuning.
Race Director
Joined: Apr 2003
Posts: 17,699
Likes: 1,667
From: moraga ca
On a stock motor, I would think the 58mm would require a tune to work well. The tps senses a throttle position change which is different from a stock throttle body compared with a larger one. A large one will let in more air for the same throttle position change and possibly give you the flat spot you are experiencing.
Safety Car
Joined: Sep 2000
Posts: 3,524
Likes: 4
From: Hinckley Ohio
I have no mods yet. I was informed that this TB would be the way to go as it is not a "re-made" piece, that it's a fully machined unit and as I start the mods, it would be a great addition. When I inquired as to any difficulty on a stock motor - I was informed this shouldn't be a problem for now. It is not a huge problem if it is going to go away as mods get done, but if not, this would really suck.
The mods planned for next season are ported heads, cam, LT headers/hi flow cat/and exhaust. I will also be doing some sort of air intake mod and computer tuning.
The mods planned for next season are ported heads, cam, LT headers/hi flow cat/and exhaust. I will also be doing some sort of air intake mod and computer tuning.
In any event to just bolt a 58mm tb on to a stock manifold does create a problem.....the intake ports on the stock manifold are less than 58mm which creates two issues...
First issue is you will not get the flow of the 58mm openings since now the intake manifold with smaller openings is restricting your flow..
Second and perhaps worse is the turbulance created when the air flow hits the sharp openings on the intake manifold..
This is such an old rehashed topic.....from an old old thread probably 10 years ago someone on the forum did a baseline dyno, dyno with the 58mm tb on stock manifold, then dyno after the intake was opened up
I do not remember the actual numbers, but just mounting the 58tb on a stock manifold actually resulted in a very small loss of hp.....after opening up the intake manifold there was a small, but nice increase in power..
BTW I have no dead spots with my 58mm tb..
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
At this point your $$$ would be better spent on other things that will give to instant/ not future results
Race Director
Joined: Jan 2005
Posts: 10,641
Likes: 13
From: Slidell Louisiana
First question is what motor are we talking about????
In any event to just bolt a 58mm tb on to a stock manifold does create a problem.....the intake ports on the stock manifold are less than 58mm which creates two issues...
First issue is you will not get the flow of the 58mm openings since now the intake manifold with smaller openings is restricting your flow..
Second and perhaps worse is the turbulance created when the air flow hits the sharp openings on the intake manifold..
This is such an old rehashed topic.....from an old old thread probably 10 years ago someone on the forum did a baseline dyno, dyno with the 58mm tb on stock manifold, then dyno after the intake was opened up
I do not remember the actual numbers, but just mounting the 58tb on a stock manifold actually resulted in a very small loss of hp.....after opening up the intake manifold there was a small, but nice increase in power..
BTW I have no dead spots with my 58mm tb..
In any event to just bolt a 58mm tb on to a stock manifold does create a problem.....the intake ports on the stock manifold are less than 58mm which creates two issues...
First issue is you will not get the flow of the 58mm openings since now the intake manifold with smaller openings is restricting your flow..
Second and perhaps worse is the turbulance created when the air flow hits the sharp openings on the intake manifold..
This is such an old rehashed topic.....from an old old thread probably 10 years ago someone on the forum did a baseline dyno, dyno with the 58mm tb on stock manifold, then dyno after the intake was opened up
I do not remember the actual numbers, but just mounting the 58tb on a stock manifold actually resulted in a very small loss of hp.....after opening up the intake manifold there was a small, but nice increase in power..
BTW I have no dead spots with my 58mm tb..
