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Old 01-07-2012, 12:59 AM   #1
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help

When my fox was completely stock (with 2 exhaust leaks, 1 in the exhaust manifold and one after the cat), i was running the 1/8 mile at an average of around 10.6. I recently added a 75mm throttle body with a matching egr spacer, c&l 73mm MAF, bbk shorty headers, new spark plugs, new valve cover gaskets because one was leaking, new intake manifold gasket because I had to take off the upper intake to get the valve covers off, bbk pulleys, and cleaned the air filter. I just went back to the track today and I'm running a 10.8, .2 seconds slower with all those upgrades and seals. My battery doesn't want charge normal at idle, even with the stock alternator pulley on and the engine keeps allowing down the idle is it idles too long down to close to 500 rpm. Any ideas why that could be? I'm leaning towards the belt I put on being to tight but I haven't gotten thechance to check it yet. There is no check engine light on and seems to run fine with normal street driving except at idle. Any ideas? I want to fix this problem ASAP.
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Old 01-07-2012, 01:42 AM   #2
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Re: help

honestly the mods you added won't net much of anything...the shorties were the best mod in the group, but they really don't open up that exhaust like a good set of LT's..

As for actually running what were the conditions of the track both times? the weather? how much gas were you carrying? what time of the year? Did you change anything in the suspension or tires? what psi where you running in your tires btw?

each of those questions can cause you to either run faster or slower depending on your answer...

my stock v6 runs 10.4's (well my old v6, the current one hasn't seen a track day)consistantly so don't be too down...a stock 5.0 just isn't a fast car...partly to do with the gearing in them from factory, and the low HP they come with stock..look into working on the rear and find you some GT40P heads off of a 5.0 Ford Explorer...then hit the track again. You'll be surprised how much better it runs
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Old 01-07-2012, 01:54 AM   #3
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The conditions were actually pretty similar, the last time I raced was in November and this is San Diego where winter is usually between 45 and 50 degrees at night and it shouldn't be running slower, if anything, a little faster and the charging and idle is what is concerning me, it didn't start until after I added the pulleys (i drive almost 2 months with all the upgrades other than the pulleys and it ran fine, infact, i could actually feel the difference in power, remember, i had exhaust leaks and gasket leaks that were fixed. It feels like it's not charging and maybe misfiring too and idles weird.
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Old 01-07-2012, 02:18 AM   #4
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Re: help

were the pulleys just lighter pulleys or where they different in size? you said something about your belt being to tight. I'd take a look at that tomorrow a little closer
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Old 01-07-2012, 02:24 AM   #5
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Yeah, they were different sizes, the crank pulley is smaller, by far, the other 2 were slightly bigger than stock but like I said, i kept the alternator pulley on because it didn't want to charge at all with the aftermarket pulley on. I'll take a look at it, hopefully that's the only problem but it shouldn't be thinking slower...
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Old 01-07-2012, 04:35 AM   #6
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Re: help

Quote:
Originally Posted by nickel501989 View Post
When my fox was completely stock (with 2 exhaust leaks, 1 in the exhaust manifold and one after the cat), i was running the 1/8 mile at an average of around 10.6. I recently added a 75mm throttle body with a matching egr spacer, c&l 73mm MAF, bbk shorty headers, new spark plugs, new valve cover gaskets because one was leaking, new intake manifold gasket because I had to take off the upper intake to get the valve covers off, bbk pulleys, and cleaned the air filter. I just went back to the track today and I'm running a 10.8, .2 seconds slower with all those upgrades and seals. My battery doesn't want charge normal at idle, even with the stock alternator pulley on and the engine keeps allowing down the idle is it idles too long down to close to 500 rpm. Any ideas why that could be? I'm leaning towards the belt I put on being to tight but I haven't gotten thechance to check it yet. There is no check engine light on and seems to run fine with normal street driving except at idle. Any ideas? I want to fix this problem ASAP.
Temperature and humidity conditions alone could account for the difference, much less all the other variables that come into play, such as your reaction time, the car's response time, lubricating fluid temps, tire pressure and traction differences, etc., etc.. I wouldn't stress out too much over the difference. To realize the full benefits of performance upgrades you need to tune the engine/EFI system to take advantage of them.

The under-drive pulleys are the culprit for your charging problems I'd bet.
You will have to upgrade your alternator or swap back to your stock pulleys.
Just changing the alternator pulley may not be enough to do it.
But first have your alternator checked to be sure it is charging correctly.

At idle your alternator is not putting out enough voltage/current, therefore it is likely the cause of your erratic idle because the system is not seeing the proper voltage.
The belt being to tight will put too much side load on your engine and accessories' pulleys eventually causing bearing damage and failure.
It should not cause charging problems unless it has already damaged the alternator bearings and the alternator rotor is dragging, slowing it down even further. However you should be able to notice the adverse effects, such as belt squealing or smoking from slipping over the alternator pulley.

Note: Exhaust leaks in the system before the O2 sensors can cause the sensors to give false readings affecting the tune of your engine.
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Old 01-07-2012, 07:13 AM   #7
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Quote:
Originally Posted by Trojan Horse

Temperature and humidity conditions alone could account for the difference, much less all the other variables that come into play, such as your reaction time, the car's response time, lubricating fluid temps, tire pressure and traction differences, etc., etc.. I wouldn't stress out too much over the difference. To realize the full benefits of performance upgrades you need to tune the engine/EFI system to take advantage of them.

The under-drive pulleys are the culprit for your charging problems I'd bet.
You will have to upgrade your alternator or swap back to your stock pulleys.
Just changing the alternator pulley may not be enough to do it.
But first have your alternator checked to be sure it is charging correctly.

At idle your alternator is not putting out enough voltage/current, therefore it is likely the cause of your erratic idle because the system is not seeing the proper voltage.
The belt being to tight will put too much side load on your engine and accessories' pulleys eventually causing bearing damage and failure.
It should not cause charging problems unless it has already damaged the alternator bearings and the alternator rotor is dragging, slowing it down even further. However you should be able to notice the adverse effects, such as belt squealing or smoking from slipping over the alternator pulley.

Note: Exhaust leaks in the system before the O2 sensors can cause the sensors to give false readings affecting the tune of your engine.
Agreed.I had the same problem.if u leave all ur other pulleys on ur gonna have to use an overdrive pulley on ur alternator that is smaller than the stock pulley.
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Old 01-07-2012, 09:49 AM   #8
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Originally Posted by dreamstang

Agreed.I had the same problem.if u leave all ur other pulleys on ur gonna have to use an overdrive pulley on ur alternator that is smaller than the stock pulley.
Also I think u can use a high amp alternator .
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Old 01-07-2012, 05:20 PM   #9
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Yeah, i was planning on upgrading to a 130 amp alternator anyway, i was just hoping I could keep the stock alternator as long as possible but it looks like I'm going to have to change it sooner than I wanted to.
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Old 01-07-2012, 05:45 PM   #10
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Originally Posted by nickel501989
Yeah, i was planning on upgrading to a 130 amp alternator anyway, i was just hoping I could keep the stock alternator as long as possible but it looks like I'm going to have to change it sooner than I wanted to.
Like I said u can still change to a smaller than stock pulley.this way kind of defeats a little of the purpose of being underdriven.but the other accesories will still be.I got a overdrive pulley from summit racing and now it charges perfect.you will have to get a different belt though.
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Old 01-07-2012, 07:00 PM   #11
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There could be a bad cell in the battery not keeping a good charge you can check the the batt by disconnecting the batt while it's at idle the car should run and drive with the batt out of the car if the car instantly dies you need a altn but if it stays running get the batt tested. You also use a screwdriver and put it about a inch from the back of the alternator you shoul feel a magnetic force pulling it The pull should be strong if the alternator is working the way it's soppose to. Both of those are Back yard ways a voltage meter is the best
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Old 01-07-2012, 07:10 PM   #12
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Ok, yeah, i need to get that checked but I just went out and looked at my car and I guess I forgot to tighten one of the battery cables all the way (the positive one) so I tightened it and the idle was a little less erratic but still bounced around a little and the charge was a little better but still moving a little at idle. I'm just going to take the pulleys off and put the stock ones back on until I get a more powerful alternator that can charge it better. I think that should fix my problem but we'll see, thanks everyone for the input and advice.
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Old 01-07-2012, 07:33 PM   #13
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Originally Posted by nickel501989
Ok, yeah, i need to get that checked but I just went out and looked at my car and I guess I forgot to tighten one of the battery cables all the way (the positive one) so I tightened it and the idle was a little less erratic but still bounced around a little and the charge was a little better but still moving a little at idle. I'm just going to take the pulleys off and put the stock ones back on until I get a more powerful alternator that can charge it better. I think that should fix my problem but we'll see, thanks everyone for the input and advice.
Good.that is the best way.
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