So I have the Pettit kit with the larger pulley on the alternator. I just got an upgraded alternator from IRP and swapped the pulleys.

Question is.... in your humble opinion would you

1. run it, log it and see how things go?
2. Get an additional pulley like the pineapple, RP, or whoever's pulley and go back to the smaller pulley? Which should still leave enough contact on the water pump pulley (probably more than I currently have).

If option 2 anyone know what size belt? Like anyone have the same setup?

I believe this will fix my problems with an leaning issue when things get hot as my other alternator was not pushing over 13.5 volts at high boost high rpm after so many pulls.

Thoughts?

 

Had the same voltage issue when I was running the GReddy kit, I think I have seen low 13V at idle in a soaked engine bay even with IRP alternator. I've moved to Banzai Racing pulley kit and FFE idle pulley since, now my lowest idle voltage is around 13.7V, and usually hit 14V as soon as it gets moving. Belt is length is going to depend on your idler setup, and with or without A/C.

 

Wow 13 is pretty damn low. I was 13.6-13.7 at idle with the new alternator. Looked at my max off the commander after a quick drive today at 7100 rpm it hit 14.6 which I think is higher than my old one ever got...
I have A/C. I was thinking I would be able to put the smaller pulley back on the alt and just add the idle pulley as to keep enough tension on the water pump. I could call RP tomorrow, or Pineapple or someone I guess. I do not want voltage to be a cause of going lean when I have added mass grounds, re wired the pump, etc.

 

Yeah, I think 13.2-13.3V sitting in traffic during high 90F weather, with radiator fans running.

 

Definitely no good.
I will call Pineapple tomorrow and see what they recommend. If I can put the smaller pulley back on that would be awesome. I can try to call IRP, but haven't had much luck as they are swamped.

 

You guys may have something more going on than just a pulley issue. I'm using a stock alternator that's who knows how old with a smaller pulley from banzai, a tiny magna power battery and my voltage never dips below 14.2 under any circumstance. I've ran a new wire from my alternator to the fuse box. Maybe that has something to do with it. You guys might want to look into your wiring instead

 

The smaller pulley will turn it faster. I am usually around d 14 at idle, but it does dip. I will be doing some logging today, so I hope it looks "ok".

My batt is new, all wiring looks awesome and tests proper. The wires to the alt look brand new, I have put a plethora of grounds in the proper location, the battery is relocated, but again has beautiful wires, and extra grounding.
The pump has been rewired from the batt and extra wire added through the bulkhead.

 

First off, you need an idler pulley. Looking at the picture you don't have an air pump and you are running a short belt on the alternator/water pump. You need an idler pulley for proper belt contact with the water pump pulley. Pineapple Racing, RP, and Full Function all make some nice idler pullies.

That said, there's just no good reason to run weird size water pump and alternator pulllies There are aftermarket ones out there that are same diameter as stock. A lot of the old school pulley kits were to get some belt contact with the water pump before idler pullies came along. Even with those you have a water pump that can easily slip - I bet right now with the car off you can easily turn that water pump pulley by hand.

Going with an under drive main pulley can net some power increase but often at the expense of low idle voltage. Good on a track car, not so great on a street car. I had one once - put the stock main pulley back on, it's just not worth it.

Dale

 

Thanks Dale,
So you would go back to the oem size alternator pulley with an idle pulley and should be able to leave that water pump pulley? Sorry not dealing with pulleys and belt sizes often it gets confusing to me.
Yes I can turn the water pump easily by hand when it is cold. Not at all or not so easily when it is hot. I have 0 cooling issues at the moment, but wouldn't mind some extra contact.

 

You can keep that water pump pulley no problem. Once you get the idler pulley on that will give enough belt length that you will be on a pretty common size.

For the belt you may just need to make a few back-and-forth to the parts store to get the right size. Banzai Racing has a list of belt sizes on their web site, that can at least get you a starting point.

Dale

 

I Will order today.

 

To clarify: a smaller pulley will spin slower...the opposite was stated above

So the alternator is brand new and you're still getting low voltage readings? I would check the wiring, my charging issues were wire related, specifically the wire that runs from the alternator to the gauge cluster

 

The bigger alternator pulley will underdrive the alternator, that was the problem. Banzai kit has the OEM alternator pulley size, and that's what I'm running now. As far as idle voltage, I've never own a car that idle hot at 14V+ lol, all are high 13's as the alternator is supposed to dial down the output when it is hot.

 

No, smaller pulley spin faster on the alternator or water pump, smaller main pulley will underdrive the whole system.

 

you're right, brain fart

 

Really for my problem this is all irrelevant I guess. My problem is high rpm/high boost. There is no way this alternator is not at max output at 7k engine rpm unless the belt is slipping or something which I believe it is not. I may get an idler pulley and put smaller pulley back on just for the hell of it, but it will not fix my problem... what is it? 2k shaft rpm on alternator should be making max power?

 

Your initial post wasn't clear on the problem you are having.

Are you seeing/logging your voltage dropping at high RPM? What kind of mods do you have?

Large fuel pumps and large coil packs do pull a LOT of juice. They will pull more under load/high RPM than at low load/idle. Alternators are basically doing all they can do just off idle - that's the total output they will put out regardless of RPM. If you are seeing a voltage drop that means something is pulling a lot of current. Not going to be a pulley problem or an under drive pulley problem under this scenario.

You do need an idler pulley regardless, they are just a good idea. You also typically have to crank up the belt tension with an under drive pulley/no air pump setup which is hell on the water pump bearings and engine stationary gear bearings. I've seen real-world cases with damage that could have been prevented with an idler pulley. Of course this is a relatively new development in the RX-7 world and we destroyed a lot of pumps and bearings back in the day

Dale

 

I hope this doesn't double post. My initial problem is on thread "an ever leaning trend". After burning through 3/4s tank of gas I will start running lean in high boost/rpm. Very gradual, but it climbs. I saw the voltage was having a hard time maintaining anything over 13.5.

Mods that draw power are
1. Supra pump rewired with added grounds and wore through the bulkhead
2. Water meth on full blast at around 10psi.
3. 2 Amps for stereo, but I do not have the stereo on while logging, but the amps are technically on.

That's about it. The upgraded alternator should handle it all not with no problems.
All wiring looks good and added grounds, etc, etc.

I will get the pulley for the other reasons you specified and thx for reminding me. Pineapple reminded me of the same thing today also. Such a cool guy.

 

Possible the pump is running hotter as the gas level drops. Hands down the problem is in your gas tank with the going lean at 1/4 tank of gas.

I'm not a fan of the Supra pumps, nothing in particular, but no reason to use an OEM pump when you really should be using an aftermarket pump that's more up to the job. I'd get a Walbro 255 from Banzai Racing, swap that in, make sure it's installed properly, and see how it does. They aren't very expensive and you wouldn't be out much time and money to try it.

Dale

 

Dale I think your on to something for sure, or it is possible the O-Ring sucking in air? I will get rid of the oem O ring thing and install a hose

 

The OEM O-ring works wonderfully. An O-ring can make a tighter seal than any hose clamp can provided it's installed right. There's pictures on how the o-ring should be installed with the plastic spacers that support it.

I'm not a fan of hacking up the stock hanger for a hose/hose clamps unless absolutely necessary. My Walbro has been on my car for 12 years with the OEM-style O-ring with ZERO problems.

Dale