Every time I've used the two step for building boost while testing the setup- (spark cut rpm, spark retard rpm) - I experienced very rough Idle even though I only ran in the boost building "mode" for ~ 2 seconds.
I realize this is very abusive to the turbo, manifold etc. but I'm asking why does the car Idle rough for 5 or 6 seconds after doing this? Its not rough as in improper mixture, it is rough as in a couple of spark plug wires off.

Anyone else experience this?

I have a theory as to what is going on but I might be wrong.

JDB

 

Can you post a log of this happening? What are your 2-step settings? Any anti-lag in the mix? I can think of several reasons, but its hard to say without seeing some data.

 

I might be able to dig some up but I can't imagine what they would reveal.
A misfire shows up initially as a lean condition but the root cause would not be known from a typical data log IMO.

There was no WB FB compensation being allowed during these tests. It was running only from the map.

JDB

 

2 step ignition cut 5500
2 step retard 5450 <-------this is the important one
2 step ok below vss 2

 

Possibly because while you are running the 2step you are running very rich? You still have fuel but are retarding then cutting out ignition. I would think this would coat the plugs in some pretty sooty stuff. Maybe it takes a couple seconds for it to burn off.

I think that your AFR log will not tell you this is happening in the ENGINE, because the extra fuel is still burning, just not in the engine, but rather in the exhaust manifold or in the turbo.

BTW, how much boost are you building? I am making 10psi with the following settings:
2 step ignition cut 4700
2 step retard 4500
2 step ok below vss 5

and it does not seem to be too hard on the turbo system. No big backfires or anything.

Interestingly, I seem to be able to launch harder with this setting:
2 step fuel cut 4700
2 step ignition cut 10000
2 step retard 10000
2 step ok below vss 5

it makes 0 boost, but still seems to launch pretty strong.

Good Luck,

EVOlutionary

 

I cannot agree with your theory that the mixture is rich and therefore coating the plugs in a matter of seconds. A/F ratio is correct............burned or unburned.

I've seen over 15 psi.

I think the fact that you are able to launch better with no boost on the other setting is a very important point.

Thanks for your input.

 

No Problem. One more question - when the 2step pulls timing (to create boost) does it throw all the timing back in as soon as you hit 2mph, or does it add the timing back over a period of time? If it is the latter, it could contribute to the rough running. Do you know if we can adjust this how much timing is pulled or how quickly it is added back in?

EVOlutionary

 

please post a log.

 

It gives the timing back as soon as the RPM falls below the "retard rpm" such as when the clutch is released - OR when the set vehicle speed is reached, although I THINK this cannot recognize a speed below ~8 mph, and that sux.

 

Could that be an issue with the VSS or how the VSS is calibrated in the EMS?

 

I would be guessing If I answered that but it seems like a flaw in the setup when you think about how it works. If you turn off the 2 step based on vehicle speed............wouldn't you want it off as soon as the car starts moving?
Not at 8 MPH!

JD

 

hi evryone im new here i had my evo 7 for 3 month now and i had such hard time with boosting! the mecanic replace the turbo ( thats what he said) but the car still have problem boosting! can someone tell me why when the car is cold boost beautifully but if i stop to refill when i turn the car on again doesnt boost! how do i bilt the boost? sorry for the " stupid " question but i try to learn how to use my evo! never had a turbo car before ! thanks

 

How exactly did you end up in this topic?

 

My two cents I saw that when I did the 2 step and was making more than 10psi the car would do the same...And the problem was the headgasket..It was blown and the head was rising and boost was moving from one cylinder to another and the car would retard ...check your car for a headgasket ...

 

i experienced the same issue....the only way i was able to work around it was to set-up the 2 step like this....

2step ign cut 5200

2step fuel cut / 2 step retard rev 8300

this only builds ~10 psi on a fp-red, after ~1 second of 2step, but you can stand on it all day & you wont encounter a misifre after getting off of the 2step...

i believe i was over-heating the plugs due to severe retard of timing.

if you want more boost, i suggest using the anti lag function for your launch...this will allow you to input how much total timing you want during 2step....this gets little more involved, but worth it imo.