Eaton not putting out "right amount" of boost

[DropSVT]

Hi all this is my first post so take it easy on me and i do apologize if this is in the wrong section.

I bought a 2003 vert a couple months back which was believed to be bone stock 73k miles. I did a few upgrades (2.81 upper, bbk fender CAI, magnaflow high flow catted x pipe, bassani catback, sct x4 bama tune) hoping to be over the 450whp mark which seemed reasonable with all the fellow termi owners making much more with same mods. the bama tune was just to hold me over till i got a AED tune
Took the car to AED and first pull was 407whp :??: after tuning i made 444.4rwhp/ 467 tq SAE and was told its one of the lower hp cobras that have been on that dyno. because i was running a 2.81 upper only i should have peaked 14.5 psi and dropped back to 12.5psi but unfortunatley only saw max 12.5 which dropped back to 10-10.5 psi. Shaun said that the rotor clearance in the case may be the reason behind low psi levels and after research i havnt found much on other people having the same problem.
My question is has anybody ran into this before with their eaton? should i just be in the market for a less used/abused m112 or maybe having my blower rebuilt/ported. i respect all opinions out there.

 

[Zemedici]

Few different possibilities

Could be possible belt slip, leaky bypass valve, internal blower issues, etc. but ya gotta remember to take dyno numbers with a grain of salt. If AED said its the blower, I would trust their judgement, as they're one of the best in the industry.

It would be cheaper for you to buy a used M122, than having yours rebuilt. Of course then you're buying a used part that you truly don't know the history of, so there's that risk. It would be a good opportunity to upgrade the blower, and go with a Whipple or TVS.

 

[P49Y-CY]

444/467 for an upper only is not completely out of the norm - i'd say be happy and enjoy! the car will be a blast to drive.


+1 on trusting what aed says and recommends, they've got a great rep

 

[DropSVT]

It would be cheaper for you to buy a used M122, than having yours rebuilt. Of course then you're buying a used part that you truly don't know the history of, so there's that risk. It would be a good opportunity to upgrade the blower, and go with a Whipple or TVS.

I'll have to look into getting my hands on a good condition m122. For the next year or two my power goal is only 500 to the wheels, which i'm not too far from. A whipple is in the distant future but Im in no rush to spend 3k+ unless all these gm cars start are beating me lol

 

[DropSVT]

444/467 for an upper only is not completely out of the norm - i'd say be happy and enjoy! the car will be a blast to drive.


+1 on trusting what aed says and recommends, they've got a great rep

The car is absolutely fun to drive i must say. AED really woke my car up, I'd trust anything shaun has to say about the cobras.

 

[Zemedici]

I'll have to look into getting my hands on a good condition m122. For the next year or two my power goal is only 500 to the wheels, which i'm not too far from. A whipple is in the distant future but Im in no rush to spend 3k+ unless all these gm cars start are beating me lol

I mean M112, M122 is for GT500s and needs adapter brackets and shit to work, too much hassle. Get another M112 and have it ported.

 

[01yellercobra]

I have a 2.8" upper on my blower only see 12psi. I think the 2.76 is the one for 14psi.

 

[DropSVT]

I mean M112, M122 is for GT500s and needs adapter brackets and shit to work, too much hassle. Get another M112 and have it ported.

ahh gotcha I was doing research on the m122 and adapters and a lot of people were saying its not worth the hassle for minimum gains. looks like ill be buying a m112 and porting it in the near future.:rockon:

 

[DropSVT]

I have a 2.8" upper on my blower only see 12psi. I think the 2.76 is the one for 14psi.

ya I thought the same thing but I guess its suppose to peak 14ish then drop back a bit to 12 at the end of the band. I wish there was a way to datalog boost to put side by side the rpm band on dynographs. I'll post a dyno graph up later if I get time tonight

 

[stangfreak]

How does the car feel? 2.80 upper pulley will make 14lbs of boost. The 2.76 will make 14ish to 15lbs. My car made little over 15lbs with a 2.76. 2.93 I made 13. I have had honestly every single pulley combo on the eaton you can think of lol.

 

[Bdubbs]

I never hit 14+ psi with a 2.8 upper. Highest I've seen was 13.5 and I drive in some cooler weather like upper 40's.

 

[DropSVT]

The car feels great i feel like i should be putting more lengths on my buddys yote though. Im looking into buying a less used blower for now to make a little extra power