I've had these dyno sheets for a while but haven't had time to do much to figure out what is going on. It seems that sometime after my 3.5L conversion my top end power is suffering . I did lower the compression to 10:1 so I did expect to see a little loss from that. Also, with tthe extra .3 displacement i was expecting to lose 10-20% in boost. But as you can see its more than that. The red line in the first 2 graphs is with the 3.2L and the blue is the 3.5L. My guess on this is that i had a torn belt at the time - i only had 3 ribs of the six left on and it was probably a little too small so it was undoubtedly slipping. I didn't figure out i needed a slightly smaller belt with the hbp . Also i had a cel for a faulty tps sensor during the dyno which i replaced soon after.

My boost through the entire range is half of what it used to be (red line is with 3.2L):


I picked up pretty good low end torque (+30lbs in some spots, but more consistently +20lbs) and hp (+10 to +20)


A/F is safe, but as you can see tuning was desperately needed!

 

while the torn belt may have had a bit to do with it as it may have slipped....but im seeing smth different here... ur biggest downfall was ur faulty TPS!
The throttle opening determines
the engine’s power output, so monitoring the position of the throttle gives the computer information it needs to determine engine load......this information along with input from other sensors such as the manifold absolute pressure (map) sensors and temperature
sensors then is used to calculate the enginess fuel
requirements, spark timing and other functions. That hurt a lot of your performance...and also u did lose a bit from lower compression, but not to get below the 3.2 power output...if nothing else..a 3.5 with 10.0:1, should at least make the same power as 3.2 1ith 11.0:1

ur boost is all over the place and very unstable.... and so is your AFR.

obvioulsy you slapped a different set of pistons in that 3.5 block to bring down the comp. to 10.0:1 ...did you do a compression test? what heads are you using?

not knowing how bad that TPS was...u couldn't tell how much the TB actually opened up...air starvation? as if the SC didnt get enough air to even build boost off of. besides all that...most likely the ECU threw the car in limp mode while having a TPS code set off.

everything seems so unstable..

do a compression test, change ur belt...check ur valves, make sure they're tight to the spec...(.008 intake-.011 exhaust) even if they dont tap, check them anyway.

^^^^^ these are things more from my own way...but im leaning a lot towards the tps.

let me know!

 

........ forgot to ask....hows ur vaccum at idle?

 

not sure about vacuum at idle, i assume its fine....why?

I def don't have less power than before, just above 5k rpms that's why i thought it was the belt. But the tps was definitely screwing things up so i agree with you there but after i got it replaced it's been fine...just haven't gotten a chance to retune. The A/F is fine too...two of the squigles are the before and you can see the motor really wanted to lean out which makes sense. Upping the displacement you always have to up the fuel, so the AEM took care of that and i'm a solid ~11.8:1 alll the way thru.

I have stock heads but they've been ported and i'm running type-S cams and oversized intake valves...it might be time to have them reseated...possibly...

One thing is for sure, the mp62 does not cut it for this motor...maybe the mp90 or even a turbo will

 

you dont have less power, but you also dont have that much more...and yes, at 5k things got screwed up.... but ur boost levels all the way through, are much lower....so imagine if it was where its supposed to be. the afr is fine....i agree, it just seemed like it was fighting so much...

mp62 is supposedly for 2.0-4.0 litter engines. i dont plan on getting another blower lol

 

supposedly, but for comparisons, the 2.0 cobalt SS comes with a mp62 and the 4.8 03-05 cobra's came with mp112's.

i think its safe to say its too small for the 3.2, let alone a 3.5

usman, i think you should really start thinking about a mp90 swap, it wont cost that much at all. $275 for the mp90 shipped (new) 500 for the fabbed pieces

 

sean, i might def go that route. this time around i might wait to see some results of the different FI options out there instead of being the test car

 

Sorry to hear bro but somehow I'm not surprised, good to see you're not giving up, kudos for pushing the limits and sticking with the FI

Keep and good luck!