NitrOmm

iTrader: (1)

Recent Dyno showed flat HP after 5,800 rpm. We thought possible:
.back pressure from exhaust
.blower cavitation ( out of blower,, lol)
.belt slip
We ruled out exhaust by opening just after y pipe, no difference other than 20 HP gain. I have been driving daily for about a month now. According to my boost meter, I'm gradually losing boost after 5k rpm. Running 7lbs (2.9" pulley)
It drops gradually down to about 2 lbs between 5,000 to 6,200. still pulls hard all the way. If it helps my numbers were as follows:
(stingy) Mustang Dyno on a hot so. Fl day 470rwhp /515trq.
W/ 50 shot n2o ( intended to cool IATs). 515rwhp/570trq.
Still had same flat spot @ 5,800. I did put a manual tensioner on to eliminate belt slip. It helps a little. But still bleeds boost off. I am now thinking valve float can be the issue.
Now: I am ok with this issue if I am just out of blower. I know my set up is only good for about 500hp or so ... I'm there. However, if it could be some other issue I don't want to leave the ponies & my beloved torque on the table.
All mods in sig, the springs we used were a kit that came from comp cams along with the cam. I am embarrassed to say that I don't remember which springs we used. I have about 7,000 miles on the new build. Part of the problem is that I do not have an original Dyno to use as a benchmark to check against lost boost drop etc.. All of this came to light after the slipping clutch was replaced.
Thanks in advance for any insight.

The Alchemist

iTrader: (19)

It's pretty typical for the 112's to run out of steam with a mildly built motor. They just aren't able to move enough cfm's to feed a well flowing 6.0l motor (assuming your ls2 is stock cube), which with your cam, and heads, and exhaust, is a well flowing combo.

Weren't the 112's orignially used on the 3.8l v-6 motors?

anewconvert

Those were M90's on the 3.8. M112 was an upgrade for them

itsslow98

iTrader: (18)

That 112 is done, on a 346 they are maxed out at about 500rwhp. On an ls2 witha big cam and heads its definetly done. Time to go to a 2300.

NitrOmm

iTrader: (1)

Thanks for the feedback. So would it be safe to assume that the bleeding boost that I am seeing is the blower loosing its ability to keep up ? I just want to be sure that I dont have another issue.

The Alchemist

iTrader: (19)

Yes. Think of it this way. The blower is able to produce a certain amount of CFM of air, but as the rpms increase, the motor can process more air. So if the blower can make stops increasing how much air it can move, but the motor is increasing, then you start to see less boost pressure.

Slowhawk

iTrader: (12)

It's the blower running out of air. Highest I've ever seen out of the 112 is 504rwhp. That was a H/C setup maxxing the blower.

NitrOmm

iTrader: (1)

Thanks for The input. At least I won't be chasing a ghost at this point. For a DD, I am satisfied with performance. I am sure there will be a point when I get numb to the power ... But for now it's plenty of fun.
Alchemist: thanks for the description.

dlively11

You can get 500+ WHP with a 112 on a LS2 with stock cam, stock heads, shortys into factory cats. Takes a 2.6 pulley but plenty have gotten those numbers. Even my A4 puts down 480 WHP with a 2.7 pulley. Add a blower cam and 550+ WHP is easy.

Noticed you are on a Mustang dyno too. 470 isnt too bad although mine ran a hair under 450 on a Mustang Dyno. You really should look into getting a 2.7 pulley atleast. It will REALLY wake that car up ! Another 2-3 PSI and you will be seeing another 40+ WHP. Oh and get a ECS tensioner with a Gatorback belt. Will get rid of slip down to a 2.6 pulley.

itsslow98

iTrader: (18)

Never ever seen a 112 go 550rwhp. It just will not flow the air to do it. Your either guessing on power or are on a very very happy dyno.

Even in the case you could spin that 112 fast enough to make that kind of power, it would create so much heat the ECM would yank a ton of timing because of the IATs.

poloaa009

That 112 is done, on a 346 they are maxed out at about 500rwhp.

hellbents10

iTrader: (10)

550 with a maggie equals a very very happy dyno lol. On our dyno 500 is about it with a 112 and all the goodies.

My S10 with a 5.3l on E85 with a 224 cam did 500 through a 80e and a 3" pulley. I figured it might have hit 530 with a 2.6 or 2.7. Again that is on E85 with 24 degrees advance.

Old Geezer

iTrader: (3)

+20RW by opening a cutout??

Adam Connell

Not uncommon with blower setups, they absolutely love to breathe.

meine96ws6

iTrader: (4)

Go procharger, problem solved.. we just wrapped up an ls1 build (ecs blower cam, harden push rods, ported ls6 oil pump, ls6 intake manifold, kb boost a pump, racetronix pump, 42 lb injectors , headers, exh...

Put down 541.66 rw hp 473.xx rw tq on dynojet on 9.22 psi.

NitrOmm

iTrader: (1)

I've resurrected the thread because while recently checking IATs with a scanner I noticed that my throttle was only opening 82%. After verifying this physically, I couldn't believe that I left this unnoticed all of this time.
Car is in the shop for (yet again) another clutch issue. We have adjusted for WOT and plan to recheck the tune etc..
My question is now:
Could the lack of air be the cause of my boost drop. At 82% open on my NW 96mm its as if I'm running a 78mm TB. Now I know my blower is limited ... But can anyone address this as a possible cause ?

New Dyno results coming this week.

dlively11

The misinformation about what these blowers can make on these engines is driving me crazy. Here you go 560 on an A4 LS1 and 590 on a LS2 not sure if its a M6 or A4 ....... I am sure others have made more.


RECORDS (based on stock-cube LS1)

MP112 Horsepower Leader: ddawson @ 560 A4 trans
MP112 Torque Monster: ddawson @ 536

RECORDS (based on stock-cube LS2)

MP112 Horsepower Leader: CHA-LEE @ 590
MP112 Torque Monster: Willow @ 561

Louis

iTrader: (7)

I've made 550 rwhp on an ls1 Maggie with kooks and a cam.

82% won't hurt much. It's close to being in the shadow of the blade at that point. Not that much of an issue as one thinks.

The Alchemist

iTrader: (19)

Where are you getting these numbers from?

Just writing down a bunch of numbers doesn't prove anything.

Here:

Record D1SC procharger, stock cube ls1 : The Alchemist @ 965 T56 trans.

mike13

iTrader: (27)

What heads and cam to get 500+rwhp?