boost questions

[lexcrob]

Why do factory boosted engines fail when you turn up the boost. Specifically maf based cars like the rb! Is it only the fact that the injectors end up going above 80% duty and starve the engine. Or is it possibly that ignition timing is not planned for above factory boost level?


example:

Adding to that question lets assume its the fact that the injectors run out of fuel. What if you stuck a BIG T4 turbo and only ran a boost level equal to stock engine output so like 4psi. Is the factory timing adjustments and fuel only related to the (amount of air) cfm entering the engine so technically it would run fine tune wise?

[talonp]

There are built in limits of adjustment on the factory ECU so it would not be able to compensate for that big of a change in the map. It would run decent out of boost if you needed to drive it to the tuning shop but as soon as the air flow went past the accepted rate of the ECU at that RPM the car would go into limp mode, Or just shoot a rod through the block. The factory allows for a certain % of deviation of the tunes because there are obviously different driving conditions across the US. Temperature, Altitude, Octane availability, blah blah blah. When you increase boost you are pushing your ecu to the edge of that accepted % deviation and, in the right circumstance, your ECU may not be able to compensate.

^^^Just a guess someone correct me if I'm wrong but it sounds good!^^^

Bottom line is when you push a car past what it was made to do you sacrifice reliability. All engines are different and some will be more prone to have different problems than others so its hard to pinpoint the exact issue. I think its safe to say that knock is the main problem which could be timing or octane. Having said that you can increase boost pretty darn safely on most engines you just have to do your research.

[OutToWinPAHC]

We are talking about a maf based non tunable ecu. What do you exspect?

[Darius]

Why do factory boosted engines fail when you turn up the boost. Specifically maf based cars like the rb! Is it only the fact that the injectors end up going above 80% duty and starve the engine. Or is it possibly that ignition timing is not planned for above factory boost level?


example:

Adding to that question lets assume its the fact that the injectors run out of fuel. What if you stuck a BIG T4 turbo and only ran a boost level equal to stock engine output so like 4psi. Is the factory timing adjustments and fuel only related to the (amount of air) cfm entering the engine so technically it would run fine tune wise?

Factory turbo'd engines do not fail simply because you turn up the boost. It makes no difference whether it is a carburated, fuel injected, DI, maf or speed-density system. They fail when you turn up the boost past what the stock fueling system can provide enough fuel to keep the engine from leaning out. Leaning out = detonation = BOOM! Reducing ignition timing will decrease the chance for detonation, but it will come at the sacrifice of power, so why bother turning up the boost in the first place?

And as far as installing a BIG T4 turbo and running low boost for equivalent power=equal air flow as a smaller turbo at higher boost pressure, it is possible. However, the T4 would be laggy and may surge because it is operating to the left of its surge limit. This is a really dumb idea BTW. Nobody with half a brain would do this and not add fueling and tuning upgrades.

[lexcrob]

Just trying to get some concepts down or though my thick head.

Ive been surfing around and see all kinds of numbers from rb20's trying to make the most power with the least money without blowing it the never ending chase i guess.

heres a good one:
rb20-dyno-t356102.html

Then ive seen a few 300hp ones floating around with safc's.



Just finished a compression test on my new one #1-5 (145psi) #6........ 12psi
Still starts up and runs great no smoke or anything. I know what that tick noise is now!

[OutToWinPAHC]

Your not planning on running that motor are you?

[Carl H]

safc is not going to get you to 300hp but will get you a nice hole in a piston.

300 on a 20 means big injectors, z maf, at LEAST a t3t4 57 trim, a proper tune,and a boat load of boost.

[lexcrob]

I pulled the motor and trans out this weekend. Found a big sticker on the ecm that said REPS Rapid Response & High Performance Modification by S I F T. Also has a serial cable adapter thingy on it wired into the harness im assuming consolt communication. I took the screws off for the ecm cover and the top board and shur enough S I F T sticker on the Eprom chip....... some kind of daughter board doesnt look like nistune.

I did some searching on google found squat ......

It is a 32 pin socket soldered in so possilby nistune will still work? Previous owner had no idea it was on it hidden under the carpet lol...

[lexcrob]

The above was purely an example. My buddy got a MBC cranked his sr20 in stock trim up to 19 psi. ran it for couple weeks even threw down a 8.4 in the 1/8 mile then BLEW THE TURBO AND MELTED A PISTON. He now has a brand new wrx with 3400 miles and just cobb flashed it....MONEY TO BURN IS NICE!

Im aware of what not to do for most part. I just pondered how the heck it held together for so long and exactly what caused failure.
--- fuel system simply went above 100% duty and slowly not enough fuel above a certain power level.

maybe simply bumping fuel pressure to say 65 psi could have held it together for a while.....NOT a solution but maybe better than the above...

[lexcrob]

Your not planning on running that motor are you?

Yep im that guy im gonna get spool performance kit for 2200$ and light it all on fire the first pull i do with 87 octane so i dont knock..............

[Carl H]

i'm curious about this ecu. can you email pics to me?

[lexcrob]

[lexcrob]

I searched more last night can't find anything about it. Maybe its just really old and the information is off the web?

[Carl H]

looks like you've got an rb20 ecu thats been remapped for use on a 25, as far as the other board is it tapped into the harness at all?

[Yellow4g63]

just sold my Nistune ecu last week. The ecu tune prob had some aggressive timing maps on it.

[lexcrob]

looks like you've got an rb20 ecu thats been remapped for use on a 25, as far as the other board is it tapped into the harness at all?

The engine it came off of is a rb20det its been runing it since he bought it 2 years ago. NO 25 IN THE EQUATION UNLESS U MENT PUT ECM IS FROM A 25.....
Is there anything out there that I can tune it with? I guess nistune doesnt use eeprom so wont work with it? At least not a 32 pin dip chip.



Yes, the board is wired into a couple things in the harness ill look at the pinout and let you guys know.

[lexcrob]

looks like you've got an rb20 ecu thats been remapped for use on a 25, as far as the other board is it tapped into the harness at all?

Ive got an rb20det and its the ecu that was running it?


Yep, its wired into a bunch of stuff ill get a pinout and let you guys know whats up with that.

So nobody has heard of it at all? I mean i can't even find anyone that put a dip chip inot an rb20 ecm. I believe nistune is not and eeprom dip chip?

FOUND THIS FORM 2006 eprom-tuning-project-20-s-25-s-26-s-t110940.html


Doesnt really get anywhere but says rb25 ecm no chippable. rb20 and rb26 are> That blows i was hoping id saved couple hundred bones guess i still gotta buy.....nistune or play with the box of matches an safc.

[Carl H]

was under the impression that the motor was a 25, thats all.

the daughterboard is most likely a decoder board as the rom on the chips is probably scrambled, jwt does this to their rom tunes as well.

[lexcrob]

was under the impression that the motor was a 25, thats all.

the daughterboard is most likely a decoder board as the rom on the chips is probably scrambled, jwt does this to their rom tunes as well.

So this is old school and should be bin'd in favor of nistune? No one knows where this REPs place is or came from and no one chips rb20 ecms except jim wolf? nistune is the only answer?

[Yellow4g63]

real time tuning = nistune. if you want to pull the chip and burn every change then you can prob just do it yourself with a rom burner and freeware software.

[Carl H]

if you want to send the ecu to me i can pull the rom and find out what its tuned for.
pm if interested.

[Carl H]

you need to enable your pm's man...or email me.

[lexcrob]

jeezzz im a chump

ENABLED...........

[Carl H]

still disabled man...just email me. its in my profile...

[lexcrob]

i didnt hit submit its good now