In need of some advice on a lower

[mj8]

Ok here's the deal I am running a 2.76 upper with one idler and I am hitting around 13.5 psi. I would like to get the most out of my ported Eaton which from what I hear is around 16.5 - 17 psi.

Should I add a 2lb lower and hope for 15.5 psi or should I put the 4lb on and hope for 17.5 psi? How much benefit should I expect out of those 2 extra pounds, is it even worth the trouble...trouble being new alt pulley and possibly pegging the injectors. BTW, I am looking to keep the stock injectors for now unless it's my AF ratio goes way north, but I do have a BAP and a MAF-X already in place. Also I have read a lot lately about which alt pulley to use but seems as if some people are having better success without using them. :shrug:

 

[Mr. Freeze]

im on the fence on this issue too, but leaning more towards the 4lb lower when i get the supporting mods. going. ttt for ya' would like to know the benefits of those 2 lbs. also,

 

[mj8]

thanks Freeze maybe someone will chime in tomorrow...btw check out the replies over on the modular may help you out some as well. I think I may just go 4lb and bow up and get some injectors...well see.

 

[- Aj -]

/offtopic/

Hey mj - how is traction now?

/endofftopic/

 

[mj8]

/offtopic/

Hey mj - how is traction now?

/endofftopic/

Traction...what traction...LOL

Traction = None...tell me again why I want more power? :bash: :bash:

I have 315 Pilot Sports and they really just like to spin, however this is at 35 psi. I have yet to air them down to see how they would hook I may need to try that.

 

[- Aj -]

Damn. I know you have springs, what else do you have for any attempt at traction?

 

[mj8]

I have the BF IRS brace for protection but no mods for hooking yet. I hope the 315s will hook on a warm day with low pressure.

 

[knowfreed0m]

3lb lower is what I would go with.

 

[IronTerp]

The 4 lb lower will get you 16.9 psi of boost when in conjunction with a 2.80 upper according to Mosoniac's chart.

I've been running a 4 lb lower now for 7,000 miles with factory alternator pulley, (knock on wood!!!). This issue can go either way......stay with the factory 2.60" alt pulley and you'll "overspin" the alternator by 13.16% or go with the 3.20" alt pulley and you "underspin" the alternator by 8.06%.

Thus, the decision should probably rest with how you drive.......if you're more conservative, lot of city driving w/ lower rpms, keep the stock alt pulley IMO. If you like consistently cruising on the highways at 90 mph and hit the track for 80 runs a year, you may want to witch out to a 3.20".......

 

[TRBO VNM]

I have been on 2.93 upper and 6# lower for a while and stock alt. pulley. I do recommend the alt pulley to a setup like this, but not with a 2.93 upper and 4# lower. with the 2.76 upper and 4# lower I would say go with the alt. pulley to be safe. I would recommend chaning though and going with the setup I had if you are looking to the extreme. I think I got peak 19# out of it on a ported eaton.

 

[I-CAN-STANG]

I've been on the fence about the 2.76 and 4lb. lower but I think that's the setup I'll end up with.

 

[CobraBob]

The 4 lb lower will get you 16.9 psi of boost when in conjunction with a 2.80 upper according to Mosoniac's chart.

I've been running a 4 lb lower now for 7,000 miles with factory alternator pulley, (knock on wood!!!). This issue can go either way......stay with the factory 2.60" alt pulley and you'll "overspin" the alternator by 13.16% or go with the 3.20" alt pulley and you "underspin" the alternator by 8.06%.

Thus, the decision should probably rest with how you drive.......if you're more conservative, lot of city driving w/ lower rpms, keep the stock alt pulley IMO. If you like consistently cruising on the highways at 90 mph and hit the track for 80 runs a year, you may want to witch out to a 3.20".......

Excellent advice!

 

[Mr. Freeze]

The 4 lb lower will get you 16.9 psi of boost when in conjunction with a 2.80 upper according to Mosoniac's chart.

I've been running a 4 lb lower now for 7,000 miles with factory alternator pulley, (knock on wood!!!). This issue can go either way......stay with the factory 2.60" alt pulley and you'll "overspin" the alternator by 13.16% or go with the 3.20" alt pulley and you "underspin" the alternator by 8.06%.

Thus, the decision should probably rest with how you drive.......if you're more conservative, lot of city driving w/ lower rpms, keep the stock alt pulley IMO. If you like consistently cruising on the highways at 90 mph and hit the track for 80 runs a year, you may want to witch out to a 3.20".......

how much more boost does a 2.76 w/ 4lb lower get? in comparsion to the 2.80 w/ 4lb lower? i have a 2.80 pulley & thinking i should just go w/ a 2.80 w/ 4lb lower to stay safer?

 

[ChicagoMike]

2.93 upper and 4lb. lower or 3.1 upper and 6lb. lower.

If you go more aggressive than above, you will lose more HP and gain more TQ. The more aggressive you spin the eaton, the more TQ you make.

Example, friend has a 1.5 year old Steig port and is only running a 2.93 non-slip billetflow UPPER + 4 idlers, STOCK lower - he is pulling 498 rwhp and around 470 TQ on regular 93 octane gas, street tune. The more aggressive you boost it, the sooner the power curve will drop off at high RPM. I think my above suggestions are a good balance for strip and highway.

Oh... and smaller than a 2.90 upper = hello belt slip. Like Doug from BilletFlow told me - you want the bigger upper and biggest lower for max belt grip. Smaller upper = less surface = less grip = slip.

So heck, 8 lb. lower and 3.1 upper too! But ... you need a 3.7 alternator pulley (horsepower by hermann) and you're really going to be spinning the hell out of your water pump (go electric!)

Mike

 

[DirtyHarry]

I am also considering the 4# lower combo with my 2.76 upper but have the same concerns. I am curious what you decide and how it works out for you. I am told by the tuner that I best replace the alt pulley and should not need any injectors or other upgrades.

 

[o4cOb|2a]

I have a stage 3 port with 2.76 and 2# lower and the boost sees 17#'s on a cold night but on average around 16#s on a hot day. If you get an interchangable lower pulley system you can just buy extra rings if you want to switch up the boost. I think I might switch it up to a 4# lower but we'll see what she dynos at with just a 2# for now.

 

[IronTerp]

how much more boost does a 2.76 w/ 4lb lower get? in comparsion to the 2.80 w/ 4lb lower? i have a 2.80 pulley & thinking i should just go w/ a 2.80 w/ 4lb lower to stay safer?

It's only a 1/25ths of an inch difference in diameter between the 2.76 and 2.80 so they're virtually interchangeable. Really depends on which manufacturer you want to go with......Billetflow goes the 2.76/2.93/3.10 interchangeable ring route, while Reichard goes with the one piece 2.75, 2.80, 2.85, etc, route, in increments of .05" all the way up. They have the same ultra grip design.

 

[Silver03]

I got slightly better dyno numbers out of a 2.93/4lb compared to a 2.76/4lb. It was also 105* in the dyno shop at the time so maybe the 2.76 would be better for winter time. I think the 2.76/4lb was just producing too much heat in that hot of weather. I think someone else should do a comparo too and I will make it back to the dyno and test the 2 out now that temps are down in the 60's.

 

[MoreBoost]

With my 2.76/4lb and port I'm getting 506rwhp and 543 rwtq.

 

[mj8]

With my 2.76/4lb and port I'm getting 506rwhp and 543 rwtq.

Do you have any idlers? What belt are you running?