Who s running underdrive pulley Any problems experienced particularly on track

[stradman]

Really as question above.
As I mentioned in another thread, my engine shut down at the track after a few hard laps with a voltage problem. I'm currently investigating however it seems to have suffered from low alternator output which shut the engine down. Now my car only has 1500 miles on it and an underdrive pulley had already been installed on the car when I bought it.
It really sounds strange to have an alternator fail in a one year old car, but possible I guess. Battery is reading 12.5 Volts and was all charged up on tender the night before. Currently have alternator out and getting it checked by a specialist. But I also came across this article from guys who don't like underdrive pulleys.;
https://www.powerbastards.com/articles/underdrive_crank_pulley.asp
So I don't know tbh, so just asking if anyone has had any problems-particularly when running car hard like a track etc thats all.

[Stealth78]

Funny you just posted this as I literally just posted in the GenIII/IV section about trying to figure out if Jon B offers one for the GenIV. I ran one for around 20,000 miles on one of my GenIII engines before and never had a single issue. I have also read others saying they don't like them...???

[Stealth78]

Just remembered I have one right now on my SRT Ram. Never have had an issue.

[ACR Steve]

Not sure what you really gain from one . Take what they say divide by half and see if it with the risk and effort. I would leave it stock

[Stealth78]

Not sure what you really gain from one . Take what they say divide by half and see if it with the risk and effort. I would leave it stock

They are good for 10rwhp on a GenIII. This is not a made up number. I've had them on two vehicles and I know two other people who legitimately did back to back dyno runs with no other changes, both gained 10whp.

[ViperGeorge]

Someone dyno'd before and after on a Gen5 and I seem to remember they gained 15HP. In terms of track use, I never had any problem with my TA 2.0. Never noticed a voltage drop at all on the gauge. Always put out 14.2-14.4 volts. Maybe your belt is loose or slipping. Some people use a slightly shorter belt to insure it doesn't slip. I never did on my TA and the underdrive pulley still worked great.

[Bleed viper]

I have had mine on for about 3 weeks now and no issues. Charges fine, no squeaks, run good with radio, lights and a/c on. First track day was this past Saturday and ran about 4 full 30 minute sessions and didn't miss a beat. Drove the car home after the event with the a/c and radio going and no issues either. It's the IPSCO one, if that matters. The only time I've heard of it really making a difference is if you have large current draws like from an aftermarket stereo.

[Jack B]

I have 10,000 miles on my iPSCO. I put approx 20,000 miles on previous vipers with under-drive pulleys, never a problem.



I have had mine on for about 3 weeks now and no issues. Charges fine, no squeaks, run good with radio, lights and a/c on. First track day was this past Saturday and ran about 4 full 30 minute sessions and didn't miss a beat. Drove the car home after the event with the a/c and radio going and no issues either. It's the IPSCO one, if that matters. The only time I've heard of it really making a difference is if you have large current draws like from an aftermarket stereo.

[Fatboy 18]

I have a underdrive pulley on my Gen II, No problems, been on since Jan 2011
https://c1.staticflickr.com/4/3682/13697917724_68bf97d714_z.jpg

[stradman]

Well that's all reassuring to hear from you guys. I guess I'm just unlucky with a duff alternator I guess...

[IndyRon]

If you think about it there's no way an underdrive pulley can cause problems at the track where you are at elevated rpm's. I have had an underdrive pulley on mine for close to three years (G4 ACR). Twice in those three years have I noticed the voltage on the gauge drop and the lights dim slightly. Both times I was in 90+ degree temperatures idling in heavy traffic with both cooling fans operating on high with the AC on and radio and lights on at night. Other than that...zero issues.

[Voice of Reason]

I thought I read somewhere that the ACR-X cars had a UDP factory installed to help reduce/eliminate water pump scavenging? So on the track it should be a benefit not a detractor. From an alternator standpoint once you're like 100 rpm over idle it's providing a full charge so I can't see an issue there either.

[ViperGeorge]

I thought I read somewhere that the ACR-X cars had a UDP factory installed to help reduce/eliminate water pump scavenging? So on the track it should be a benefit not a detractor. From an alternator standpoint once you're like 100 rpm over idle it's providing a full charge so I can't see an issue there either.

It can also help reduce/eliminate water pump cavitation at high RPMs.

[slowhatch]

Just to echo what everyone else has already said, I've had a UDP on my gen 3 and gen 4 for a combined total of 30k miles between the two with no issues.

[dewilmoth]

Is there an obvious favorite among the under drive pulley options, or are they all the same? Seems like IPSCO is the most mentioned.

[ViperGeorge]

Is there an obvious favorite among the under drive pulley options, or are they all the same? Seems like IPSCO is the most mentioned.

IPSCO's is a very high quality part, solid billet, and could very well be the one that many vendors are selling. I know Mark J. at Woodhouse gets a lot of stuff from them (same price as buying direct from IPSCO).

[ACRucrazy]

Mopar Comp Coupe UDP

[Arizona Vipers]

I have no problems with mine on the track. I'm running the IPSCO with the stock belt. I heard the stock belt might squeak so I always take a couple extras that are shorter in my trailer, but have never had any issues at all.

[ForTehNguyen]

was thinking of doing this myself. I found the threads with the various DAYCO belt part numbers for the .5" and 1" shorter belts. Bando also makes a belt that is also another option to Dayco

Stock belt according to Bando is #7PK1765 (1765mm = 69.5") - http://bando.mycarparts.net/products...id=13004530092
The 68.5" belt for Bando is 7PK1740 (1740mm = 68.5") - http://bando.mycarparts.net/products...?brand_id=2491

Dayco and Bando are available on Amazon easily

[slowhatch]

Your alternator failed, it happens.

I've ran an IPSCO underdrive pulley on my last 3 Vipers with no issues.

[Steve M]

Fully realize that this thread is a bit on the old side, but after having read through the link in the original post, I thought I'd add my $0.02.

The guy that wrote that article is in the business of selling high output alternators. Of course he wouldn't like an underdrive pulley, especially if it is driving one of his alternators. Why? Any high output alternators I've ever messed with all had one thing in common: they required more RPM than the stock alternator in order to provide full output. That's not an issue if you maintain the stock accessory drive pulley, but it can be an issue if you swap in an underdrive pulley. This happened on my old Camaro with an underdrive pulley and a high output alternator - at the stock idle speed, it wasn't charging, but as soon as you gave it a little gas, the voltage jumped right up to where it should be. Thankfully, I had my own tuning software (that's where I got my start using HPTuners), so I just bumped up my idle speed a couple hundred RPMs and didn't have another problem.

So could an underdrive pulley cause an alternator failure? It is certainly possible...if it isn't providing a full charge at idle, the battery is having to kick in more juice to keep things running, so the alternator will have to work harder to recharge it as you are driving. This will put extra wear on the alternator, and could cause it to fail prematurely. There are a few people around here that have noted lights dimming at night with an underdrive pulley, but typically they've also been running A/C, headlights, stereo, etc., which is the worst case scenario for an electrical load on the vehicle's charging system. That's a tell-tale sign that the alternator isn't putting out enough juice, and there's only two ways to fix that:

1. Bump up the idle RPM (can only be done with custom tuning)
2. Put the stock pulley back in

Now do I think it caused the OP's problem? Probably not...there are enough guys out there running UD pulleys on Gen 4/5 Vipers that I'm sure we'd be hearing about alternator failures left and right if that was the case. It certainly doesn't help anything in the charging department, but the stock alternator isn't what I'd consider a "high output" alternator. At 180 amps, it ain't bad, but not high IMO.

[ViperGeorge]

Fully realize that this thread is a bit on the old side, but after having read through the link in the original post, I thought I'd add my $0.02.

The guy that wrote that article is in the business of selling high output alternators. Of course he wouldn't like an underdrive pulley, especially if it is driving one of his alternators. Why? Any high output alternators I've ever messed with all had one thing in common: they required more RPM than the stock alternator in order to provide full output. That's not an issue if you maintain the stock accessory drive pulley, but it can be an issue if you swap in an underdrive pulley. This happened on my old Camaro with an underdrive pulley and a high output alternator - at the stock idle speed, it wasn't charging, but as soon as you gave it a little gas, the voltage jumped right up to where it should be. Thankfully, I had my own tuning software (that's where I got my start using HPTuners), so I just bumped up my idle speed a couple hundred RPMs and didn't have another problem.

So could an underdrive pulley cause an alternator failure? It is certainly possible...if it isn't providing a full charge at idle, the battery is having to kick in more juice to keep things running, so the alternator will have to work harder to recharge it as you are driving. This will put extra wear on the alternator, and could cause it to fail prematurely. There are a few people around here that have noted lights dimming at night with an underdrive pulley, but typically they've also been running A/C, headlights, stereo, etc., which is the worst case scenario for an electrical load on the vehicle's charging system. That's a tell-tale sign that the alternator isn't putting out enough juice, and there's only two ways to fix that:

1. Bump up the idle RPM (can only be done with custom tuning)
2. Put the stock pulley back in

Now do I think it caused the OP's problem? Probably not...there are enough guys out there running UD pulleys on Gen 4/5 Vipers that I'm sure we'd be hearing about alternator failures left and right if that was the case. It certainly doesn't help anything in the charging department, but the stock alternator isn't what I'd consider a "high output" alternator. At 180 amps, it ain't bad, but not high IMO.

I notice virtually no difference in charging voltage with the UD pulley at idle. So I don't believe the alternator in the Viper is working harder to charge the battery.

[Steve M]

I notice virtually no difference in charging voltage with the UD pulley at idle. So I don't believe the alternator in the Viper is working harder to charge the battery.

What you said backs up the point I was trying to make, but probably failed. Let me try again:

1. OP had UD pulley installed on his Gen 5 Viper
2. OP had alternator failure
3. OP provided link to a vendor that stated UD pulleys are bad and can cause alternator failures, but that vendor specializes in high output alternators, which generally require more RPM at idle to start charging. The issue they were illustrating is certainly applicable to a high output aftermarket alternator, but the stock Viper alternator doesn't fall in that category.

So basically, if you have an underdrive pulley, and you have a high output alternator installed, you might end up with a problem. For 99% of Viper owners, this will never be the case. About the only reason you'd ever need to run a higher output alternator would be if you had a really big stereo system, and if that's the case, I'd highly doubt that person would also be running an underdrive pulley.

[ViperGeorge]

What you said backs up the point I was trying to make, but probably failed. Let me try again:

1. OP had UD pulley installed on his Gen 5 Viper
2. OP had alternator failure
3. OP provided link to a vendor that stated UD pulleys are bad and can cause alternator failures, but that vendor specializes in high output alternators, which generally require more RPM at idle to start charging. The issue they were illustrating is certainly applicable to a high output aftermarket alternator, but the stock Viper alternator doesn't fall in that category.

So basically, if you have an underdrive pulley, and you have a high output alternator installed, you might end up with a problem. For 99% of Viper owners, this will never be the case. About the only reason you'd ever need to run a higher output alternator would be if you had a really big stereo system, and if that's the case, I'd highly doubt that person would also be running an underdrive pulley.

Yes, I was agreeing with you although I could have been clearer.