dynoed today, questions???
 

https://www.rx7club.com/attachment.p...hmentid=125648

that run is at 9psi. fell to 7psi by 7500 (maybe even less)
mods are in sig. afr's around 10.8:1.

seems like a reasonable amount of power to me, but there was definatly much more potential.

as you can see the torque falls off REALLY huge after 5500... any ideas why? it's a pretty big compressor, the torque/boost shouldn't be falling off so badly....

well, since I'm off the second page allready... bump!

nobody has ANY idea what can cause such dramatic boost falloff?

turbo seems kinda laggy... boost is 9PSI at 4500RPM, 7psi at 6500rpm, 6psi at 7500RPM.

Thats all you put down with a T04b? That seems rather odd. As stated in my sig. i put down 232 RWHP and 219 RWTQ with boost leaks and a turbo that was ready to be dumped into a garbage can. Now when i dynoed, my peak Hp was at 5800rpm as well and the boost did drop.

Did you get an A/F reading at all when you dynoed? You could be really rich and thats whats cuttin your power? But somehow i dont think so.......

if you have a stock turbine and housing, you're choking your engine in the high rpms. thats why the power falls off so bad... why does no one realize that hybrid stockers suck?

duh, it's an aftermarket turbo, thus it's gotta be sweet;)

is your backplate bored out to 3"?

1) Is the engine stock or ported?

2) What is turbine A/R and turbine wheel trim?

3) What is your exhaust system size?


-Ted

as I posted above, AFR's are 10.8:1. The reason for the lack of power up high is most certainly the lack of boost up high (6psi at 7500!)

engine is stock, unknown s5 j-spec shortblock. 20" of vacuum at idle, ~110psi compression. Seems to be in really good shape.
2: turbine is STOCK.
3: exhaust system: 3" DP, 2.5" MP, 2.5" Y to dual 2.5". mufflers are 3" in and 3" out, straight through design.

not sure if this matters, I'm running the stock TMIC. going with water injection soon.
p/s and a/c are intact, but I'm sure that doesn't matter at all lol :)

There's your answer. :)
The stock turbine section is choking the flow.
This is why the torque peaks quickly, and why it plummets so quick approaching redline.


-Ted

so the stock turbine isn't capable of spinning that compressor to more than 6psi at 7000RPM?

even though on the (stock) compressor it would spin it to ~17PSI by that time if I let it (aware that that's neither good nor healthy, just that it would happen)

Have you modified your wastegate arm?

no.

all I did with the wastegate was attach it to that compressor housing and put it on the actuator.

the wastegate is ported (very much). The arm seemed to be the right length allready, like, it fit right on the wastegate lever, with no hassle or anything. I'm using a strange vacum source for the WG, not sure if that matters.

I've got it plumed with a T into one of the lines from the I/C out the back (s4 intercooler). to the MBC, then to the WG. I'm using a pretty "big" (dia) vacuum line too, not sure if that matters or not as well.

You probably will want to modify the arm by drilling a new hole, so that there's more tension on the arm. A lot of us had problems with the wastegate opening on it's own. I usually drill about 1.5cm or so (been a while) higher, then reattach.

hmm, I'll try that today! I think I can get to the bastard while it's on the car...

that would certainly explain the bit of lag in lower gears and the lack of boost up high...

1.5CM seemed a little extreme... I hammered the rod flat (boy was that a PITA lol) and then drilled a hole about 1CM further up, and put it on. the issue didn't TOTALLY disappear, but it did help significantly! I had to re-adjust the MBC after, of course... Boost is now 9.5PSI midrange and 8.5PSI at high RPM... car pulls about the same but MUCH better up high! feels like it's making peak HP in the low 7000's...

I had to take it off the car (that sucked :( ) ..... and I could have gone another 5mm at least I think, it doesn't have much tension on it really, just a tiny bit.. looking back, it was clearly too long in the stock position.

the lag seems to have cleared up a bit as well, though it still doesn't make 10PSI until 3500RPM...

did nobody catch this the first time i posted it?

No, they think they fixed it with the rigged WG rod. :D


-Ted

yeah that flapper not opening enough is definitely gonna keep that topend boost from falling off. LOL

(its the stock turbine wheel boys. you cant fix it)

I'll race you straight up car for car with my hybrid against your car. :)

Lets Race For Pinks Yeahhhhhh

you guys should race on that show they have on Speed, "Pinks".
:rlaugh:

Haha, yeah, I'm just giving Cartmill a hard time because he knows my car running on a hybrid would probably stomp his car at the moment.

However, is that turbine clipped, or 100% bone stock?

Yeah one of our local guys got to 330 whp @ 9psi w/ a hybrid but it was also clipped ;)

stock turbine 4 lyfe

wait you have 244.6 FLYWHEEL HP?!?!? man that sucks.

Originally Posted by jacobcartmill
if you have a stock turbine and housing, you're choking your engine in the high rpms. thats why the power falls off so bad... why does no one realize that hybrid stockers suck?

That is part of the equation, but his set-up can still be improved even with the stock exhaust turbine and housing.

Reducing intake restrictions (porting TB, better flowing IC and piping, ditching/re-locating AFM, etc) will help the top end as well reducing intake pressure drop means the exhaust side has to work less hard to power the compressor.