Strange I don't generally push my car beyond 5k because its a daily driver but today I am doing some tuning and logging. Today I'm discovering the car seems to fall on its face after 5.5k rpm like i have an intake restriction or something. But I have a buschur intake kit so that definitely can not be the issues.

Has any been through something like this? Is it tunable out or do i have something mechanical like a boost leak, which I will certainly test when time allows. The only other odd possibility is the HFC I have may be breaking down.

Boost: 21psi
AFR: 11.1-10.9

 

Barometric pressure recorded in your logs from the MAF sensor will tell you if there is a restriction before the MAF.

Is the boost dropping a lot at the top? With an MBC it can be difficult to keep the top end boost up with only 21 PSI midrange. Additionally 21 PSI is a little cautious unless you are racing in the desert on 91 octane?

 

Far as i can tell when my eyes are not glued to the road the boost doesn't really taper at all the MBC is doing a good job of it. I am running the 91 octane of course because "green" california hasn't moved to e85.

If you have a psi setting you think i can get away with on 91 octane I'd love to hear it.

 

Well I'm not one to ask because whilst I have broadly similar mods, it is a IX with no cat, air temps about 40F, 99 RON and 26 PSI. "razorlab" and others have discussed 91 PON timing and boost on here, might be worth a look, but I think most run a bit more than 21 PSI.

If you are holding boost, no boost leak, cat hasn't collapsed, taking good timing knock free with the sorts of AFR you mention then I would do a dyno run to see if it is really so below expectation and then think about mechanical issues further. Plugs? Does it use oil? Compression or leak down?

Can you post a full throttle log through 3rd or 4th gear?

 

I'm going to run a bunch of tests and see if its just something simple hopefully I can track it down in a couple days. I basically wanted to know if anyone had experienced something similar and found the solution.

 

Why don't you put one of your logs up so we can see what's going on and try to help you out better?

 

Sorry for the delay my power supply died on this laptop


Now that i have my logs again i can post them

All of these are up a rather long onramp uphill we have here in 3rd gear.

 

Timing seems low, even then the knock count is high, the airflow readings come up very late.

If there isn't a fault then this may be just the reality of 91 octane, but I'm not surprised it isn't feeling frisky at the top end with that log.

 

Yea considerable knock up top without excessive timing. What AFR are you tuned to? What Mivec map?

 

I think what he is feeling is the loss of torque, which happens around that 5k-5.2k RPM. Its perfectly normal, but if that bothers you get a bigger turbo that just kicks in at 5k LOL

 

Just a few observations:

1. Why are you logging uphill? Find a flat stetch of road and re-log.
2. Why aren't you logging the AFR? You have a ZT2 and Evoscan can log the ZT2, so please log your AFR so we can have a complete picture.
3. Install a fuel pump ASAP. You have an 04 Evo and a fuel pump is a must.
4. Evoscan can also log boost from the ZT2 if you have boost capability on your ZT2.
5. 21 psi of boost, if that is the correct boost, is fine on an Evo 8. But looking on a gauge and seeing 21 psi and actually logging 21 psi are two different things.

 

Why would a pump be a "must" at 21 psi on stock turbo???

 

Because the fuel pump on an Evo 8 sucks really bad.

Check out this thread

https://www.evolutionm.net/forums/sh...fuel+pump+test

 

The VENDOR thread states that the stock VIII pump flows up to at least 68psi with full efficiency. Base pressure at 0psi boost is 42psi then 1psi of pressure is added per 1 psi of boost. 68-42=26psi of boost.

In other words the thread you referenced says VIII pump will work without a problem at 26psi of boost. OP runs 21psi.

I still don't understand why it's a "must". Maybe i'm reading into it wrong.

P.S. My opinion is partially biased by the fact that i'm against vendor brainwashing i guess... I'm not necessarily talking about that pump thread but there's a lot of erroneous info out there, that exists for one reason - boost sales.

 

https://www.evolutionm.net/forums/sh...=stock+walboro

Here is another thread, but the guy is also a vendor. He was against swapping pumps on the 8, but the data he collected proved him wrong.

He also did research on the Evo 9 pump and does not recommend one for simple bolt-ons.

https://www.evolutionm.net/forums/sh...ight=fuel+pump