Drill or not a throttle body

Dzrtrat1111

Dzrtrat1111

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I just swapped my ECU from MEFI to a Holley terminator. With the MEFI, which was tuned by CBM, they had the throttle stop maxed out (screw spring limits it) and with the Holley I find I need to open the TB blade more too for the engine to idle. 
 

I read a lot about drilling an 1/8” hole in the throttle blade. From everyone’s experience, should this be done or avoided? How about cutting the throttle stop spring a bit or getting a longer screw?

For reference: GM Crate LS 376/525 with a CBM cable throttle body. 

 
Ive not heard of anyone doing that in a long time.  it was common place with the TPI motors and big cams hot rod parts, and also on early aftermarket EFI's, but with todays IAC motors, I dont think so. 

Maybe @Fullthrottleguy or @John@Outfront, may have some input. 

 
It is not common, but it won't hurt. It is one way to solve the issue you are having. The correct solution is to open the throttle blade as far as you need it while ensuring the IAC is closed. Once you get the idle where you want it you will need to do a TPS relearn as the open throttle blade is now the new "zero" for the ECU to recognize. Guess that means you should get a new screw and modify what you have.

 
Generally   you can crack the Throttle blades open a little if the engine is starving for air and IAC is at 100%. Unless you are running a small 78mm TB and big cam drilling a hole is not preferred as @Bobalossaid the IAC should handle it 

I have done a lot of Holley Term X's on lots of LS's and you can tune the IAC action to great extent. But I would start by cracking the blade open  - then do a TPS autoset in the term SW and watch the IAC, it should be in the 60-80% max - do this cold  - and  make sure you set Idle  to where it should be - I would say on the engine 850 warm will be good and if does not hunt  and the AFR is is between 13.9 and 14.7  and when engine is warm IAC position goes under 15% on that engine you will be good. IAC should be under 10% but unless you are a somewhat experienced tuner you will be hard pressed to get it there.

You may have to do that 2-3x to get it right, just make sure you set it cold every time and always do a TPS autoset afterward

 
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Don’t cut the  spring ( I assume you mean it’s crushed “ coil bound “)  Can you just get a longer screw?  No big issue to drilling a hole but do it as a last resort. 60-80% as mentioned is a good target for idle duty

 
Thanks all, I’ll grab a longer screw and see what I can do. 

Also…  the idle is currently at 1100 rpm. I got this tune from another member who has an identical setup. The Tuner set his car at 1200 rpm. 
 

My car starts/ runs and idles great, however, when you rev the engine above 3k it wants to stall on return to idle unless you help it with throttle. It also doesn’t want to start when hot without giving it a little throttle. 

 
Dzrtrat1111 said:
Thanks all, I’ll grab a longer screw and see what I can do. 

Also…  the idle is currently at 1100 rpm. I got this tune from another member who has an identical setup. The Tuner set his car at 1200 rpm. 
 

My car starts/ runs and idles great, however, when you rev the engine above 3k it wants to stall on return to idle unless you help it with throttle. It also doesn’t want to start when hot without giving it a little throttle. 
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Tune needs work if you need help with the throttle to keep it from stumbling after revving. 

 
Rockwood said:
Tune needs work if you need help with the throttle to keep it from stumbling after revving. 
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yeah  thats not  a good tune :-(  1100 rpm idle on basically a stock engine?  thats crazy  those engines usually idle at 800-850 - I like to set them at 850  it helps if both fans kick on and lights are on  especially with small 925 style batteries .

I would save the tune  and wipe it and start with the Wizard tune - its going to run better 

If you have a PC, the cable and v3 SW

Watch the numbers on the hand held and set the learn up to 80/80 and watch the compensation and drive it for 5 minutes at various RPMs emulate what a dyno tune would do - run at 3K  then accelerate to 4, then 5K in 3rd or 4th , then stop  and look at the learn table  - if nothing looks crazy  - apply the table but don't auto smooth it 

do that 5 or 10x and the car will be really close -  then drive it  through the gears doing a datalog, save the log and get one of us to look at your tune and data log ancd we'll get it to 90%-95% Likely and smooth it out. 

As long as cold start and warm start are good - you'll have a great tune

alternately  - just datalog the area it falls on its face  and liklely its an easy fix.  just make sure you are not running leaded fuel and have your 02 in the right spot and no exhaust leaks and you can get the Holley extremely close ...

 
As Alex is right on target,  mine has 27 degrees of overlap and still idles at 850 rpm with a holley, 

You do not need to drill the Holley, you can open the throttle blade to set idle, 

REMEMBER TO DO A TPS AUTO RESET AFTER SETTING IDLE.

Some idle issues might start with the IAC,  the P Term and the D term.  you can look on youtube and this will be explained but contacting @Fullthrottleguy guy and setting up a appointment to tune the car is always the best bet, 

Another issue that gets overlooked is the self tune,   this will not work with most Sandcar setups do to the length of the exhaust,  you need around 3 feet of tubing or it will read a false reading, 

It really is best to make the changes after fire up with a Laptop,  the handheld can be hard to work with. 

this is a pretty easy video to follow,   but i would still think about a retune   


If you are not comfortable about what the terms and definitions, then contact @Fullthrottleguy and have him tune it.  

 
Fullthrottleguy said:
yeah  thats not  a good tune :-(  1100 rpm idle on basically a stock engine?  thats crazy  those engines usually idle at 800-850 - I like to set them at 850  it helps if both fans kick on and lights are on  especially with small 925 style batteries .

I would save the tune  and wipe it and start with the Wizard tune - its going to run better 

If you have a PC, the cable and v3 SW

Watch the numbers on the hand held and set the learn up to 80/80 and watch the compensation and drive it for 5 minutes at various RPMs emulate what a dyno tune would do - run at 3K  then accelerate to 4, then 5K in 3rd or 4th , then stop  and look at the learn table  - if nothing looks crazy  - apply the table but don't auto smooth it 

do that 5 or 10x and the car will be really close -  then drive it  through the gears doing a datalog, save the log and get one of us to look at your tune and data log ancd we'll get it to 90%-95% Likely and smooth it out. 

As long as cold start and warm start are good - you'll have a great tune

alternately  - just datalog the area it falls on its face  and liklely its an easy fix.  just make sure you are not running leaded fuel and have your 02 in the right spot and no exhaust leaks and you can get the Holley extremely close ...
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I have the same setup and per Redline ~11 to 1200 is where these motors are happy from an Idle perspective...Crate LS376 525.  I tried to lower it to make it sounds a little better, but it didn't like it and would stall a bit easier when taking off, letting off after a hard throttle run, etc. 

I don't have much experience with these engines or tuning, but assume Redline does as they seem to tune these engines (specifically the LS376/525 crate engine) a lot. 

In short - my vote is keep it at 11 to 1200 RPM for idle as a reputable tuning company suggests that's the sweet spot.



 
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wesinls said:
don't have much experience with these engines or tuning, but assume Redline does as they seem to tune these engines (specifically the LS376/5262 crate engine) a lot. 
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Redline has a huge amount of experience with building and tuning engines. My LS tuned by Redline idles at 1000 RPM. 

 
Find the Idle that works best for your set-up. If the IAC is out of whack it can cause lots of issues with "Stall Saver" which is keeping the engine running after letting off the throttle. It is a process to work through little by little. There are settings in the Holley for IAC Parked % and decay rates which will keep the engine from stalling. However if the IAC is set too high just to maintain a warm idle then it cannot open enough to catch the engine before it stalls. There are also settings for cold start and Idle speed relative to engine temperature. A proper set-up IAC will also step up when the fans kick on and maintain your idle. With that, you need to make sure you are setting your idle (and IAC) with the fans off. As I said and everyone els said you always need to do a TPS reset/relearn after turning the screw on the throttle blade. It takes time to get  a tune dialed in. Be patient listen to the advice and ask pertinent questions. I always thing it's good for everyone to know as much about their cars as possible. Then again you could always just take it somewhere and let someone else tune it. I think you'll get it.

 
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Setting the idle high makes it very easy to get a stable idle without having to spend much time actually tuning.  It seems to me like the lazy way to tune an engine.  I wonder what the rest of the tune looks like?  I've looked a a few that were done that way and they were scary.

 
6 hours ago, wesinls said:

I have the same setup and per Redline ~11 to 1200 is where these motors are happy from an Idle perspective...Crate LS376 525.  I tried to lower it to make it sounds a little better, but it didn't like it and would stall a bit easier when taking off, letting off after a hard throttle run, etc. 

I don't have much experience with these engines or tuning, but assume Redline does as they seem to tune these engines (specifically the LS376/525 crate engine) a lot. 

In short - my vote is keep it at 11 to 1200 RPM for idle as a reputable tuning company suggests that's the sweet spot.




Also start with a Cam Calc, 

It might help you see if the idle is a camshaft or just pour settings 

Summit Cam Timing Calculator (summitracing.com)

Take away,  Educate you self on the system

There will always be people telling you that person is the best and that is just the way it is in life,,  Better your own life dont depend on what other people say, that can not be done.  

 
Kansas T said:
Setting the idle high makes it very easy to get a stable idle without having to spend much time actually tuning.  It seems to me like the lazy way to tune an engine.  I wonder what the rest of the tune looks like?  I've looked a a few that were done that way and they were scary.
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exactly  -

Only My Opinion, but Redline is a good , Chan is excellent - but also they cater to big dollar builds -

If you want a tune and will not pay to leave the car there a couple days to get cold start perfect and get the IAC tuned  (like @J Alper said) then you set the idle high and its an easy in and out tune. 

I like personally like drivability tunes, since I dune and  don't just do the drags   - this is something DuneHoon and others do, in fact most modern dynos can  do this and Redline has the best a  Pro Hub 4000 but many people won't pay for a real tune or have no idea so It seems many just  drop a "canned tune" in and make a few adjustments and do a couple pulls to get the "big number"  

That sometimes works but all engines ands crates behave A lot differently due to gearing, tires, and car weight so cheating or being sloppy is not the best way ....Doing it right, you start with running the car under load at various rpms and get the tune stable (basically zero or near zero (1-4%) correction, then you do the acceleration from 2 to 3 3-4-5,000 etc,  and when that is a nice curve them you go for the big number pulls

I am no expert but have a lot of stick time on the Holley systems, I  have been doing them a long time, I shared my Holley Flex Fuel Tables with Chan when they first started doing Holleys  he got it he got it right away, had them do a couple cars for me, he is very capable  - but they were high dollar (IMO) tunes 

 
38 minutes ago, J Alper said:





I know Chan personally, and it is not so much what a shop can do or dont do, it is what system they are comfortable with and what the system can do 

This is not a motor issue,  

and for the record the 525 has such a mild camshaft it should iddle around 750 rpms with no issues,  

REDLINE, is a motec pro, and the Mefi has its limitations on TPS and IAC tip in functions. @wesinls said he does not have much experience with this and, doing so is why the idle is so high,  @Sandkist has a high idle also form Redline, most likely because he is running a non motec system, 

If it is not the motec then i know for a fact Chan will not set the P trim and the D trim on the IAC fuction on the Holley,  and they use MSD for the Mefi and will turn of the IAC if that is the ECM you are using and that will have to have a hi ramp down rate and hi idle, 

@Dzrtrat1111   please watch the videos and talk with someone like @Fullthrottleguy,  if you have a car with a 1000 rpm idle, you pretty much got ripped off on your tune, 

my 445CI have a 244/256-108  and it idles at 850 RPM's from DuneHoone with no issues,  that is 32 degrees of overlap

The CT 525 is a 226/236-108  that is 15 degrees of overlap 

FACT at 15 degrees it should be able to hold a 750 idle with no issues,  

If someone does not know there overlap, not sure why you would even comment on what a correct target idle would be, to me you are just posting to post, 

Start with the Video it will educate you on the system and will be a good start. 

If the Joe S is to complicated this might be a better start, 

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"If you have a car with a 1000 rpm idle, you pretty much got ripped off on your tune,"

From your post you're basically telling me I should call redline who tuned my car on a holley terminator and tell them I got ripped off because my car idles high? Is that your stance here? Trying to understand your point of view - I have no problem admitting I know little to nothing about tuning, but also don't agree that a company with a very solid reputation who tuned my car is somewhat being slammed for tuning my car at a high idle...I specifically asked them when they were done tuning my car and asked why the idle was so high as I was hopinh for somethig with a little more chop - they stated at that time, that was in their opinion where this particular motor liked to be, and I'd be a fool to argue with them.

". @wesinls said he does not have much experience with this and, doing so is why the idle is so high," - What does this even mean, please explain.

 
Rockwood said:
Doesn’t the GMPP LS3/525 ECM have 750 as the target idle? Pretty sure GM knows something about engine tuning. :biggrin:
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I think its 750  - like I said I raise it a bit around 850 to accommodate the fans and lights draw on the alternator since most don't have nice 250amp alternators that charge fully at low RPM, street cars don't usually suffer that and  but use AC kick to turn the idle ton850 when the AC is on, so I follow that philosophy

I Quirk of Holleys they Hate low voltage and get really finicky and won't even start at 11.5v relaiably

 
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wesinls said:
"If you have a car with a 1000 rpm idle, you pretty much got ripped off on your tune,"

From your post you're basically telling me I should call redline who tuned my car on a holley terminator and tell them I got ripped off because my car idles high? Is that your stance here? Trying to understand your point of view - I have no problem admitting I know little to nothing about tuning, but also don't agree that a company with a very solid reputation who tuned my car is somewhat being slammed for tuning my car at a high idle...I specifically asked them when they were done tuning my car and asked why the idle was so high as I was hopinh for somethig with a little more chop - they stated at that time, that was in their opinion where this particular motor liked to be, and I'd be a fool to argue with them.

". @wesinls said he does not have much experience with this and, doing so is why the idle is so high," - What does this even mean, please explain.
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I know you addressed this to JAlper,  but  IMO - People make mistakes - No one hopefully gets butt hurt when you ask nicely - something like "1,000 RPM idle seems kinda high since the factory sets it at 750, whats the rationale to such a high idle?"  

Simple question  - should bring a simple answer and maybe there is a good reason or a BS one at least.  I get questions all the time and never mind sharing, thats what business is all about  - Like Ronald Reagan used to say  "trust but verify"

I fix Many tunes remotely that are just stupid mistakes and I make alot too :-)

 
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