I went to the dyno a while back with these mods:
B20z
'95 LS ECU
Injen intake w/cold-air extension
DC 4-2-1 LS header
Greddy Evo exhaust
B&M FPR

When I ran it on the dyno a curious thing happened, no matter how much I tried to lower the fuel pressure I kept on running really rich. At 5000 rpm the fuel curve dives sharply reaching about 11.2 at 5400 rpm where it stays constant till redline. I stopped lowering the pressure because I started running really lean down low.
Another oddity is that when I checked my timing it was at 8, so I thought maybe this is the problem but as I increased the timing I kept on losing noticeable amounts of power. So I ended up leaving the timing at 10.
I have a theory as to what my problem may be but I want to hear any suggestions that you may have without influence from my ideas.

 

Wow thats pretty strange. Not really sure what the problem is.
Your timing cant be right though..are you checking it correctly?

What did you dyno at BTW?

 

Well due to the above mentioned problems the numbers weren't too good:
135.1hp@~6300
133.8ft-lbs@~4350
The problem is that with the extreme richness up top the hp curve pretty much gets flat at 5600rpm till 6400rpm at which point it starts to dive. The flatness corresponds almost perfectly with the fuel

I don't have a timing light so the guy at the dyno did the timing and he is very exerienced with all types of engines including hondas


[Modified by Muglit, 10:41 PM 12/3/2001]

 

That is pretty low.

Here is my dyno with similar mods. I had the same intake, a DC 4-1 header, Tanabe exhaust and the B&M regulator with the fuel pressure set at 36 - 44 psi.
That is how I got some gains between the first and last run...turned the fuel pressure up.

 

HX_Guy,
Well I guess I'll tell my suspicions now because it is kind of based on your dyno plot you were using a DC GSR 4-1 right.
I think that it is my header, I think the DC LS header is too restrictive for the B20. I think it is not allowing for the exhaust gases to get out up top thus diluting the intake charge creating the rich reading.
I think this might also explain why it gets worse as I increase the timing. I am thinking about getting a DC USDM ITR header. What do you think?

 

No I was using a USDM 99-00 SI header..I doubt there is that big a differance between what I was using and yours.

If anything, get a JDM DC 4-1.

 

I see what you are saying that they may not be that different but that is the only thing I can think of.
As far as getting the DC JDM, I thought about it and I don't know if the cost (header+cat, ~$600) is worth it if I am not gonna build the motor for high rpm. Because the 2.5" collector headers lose power until ~5500rpm. So I was hoping that the DC USDM ITR header would cure my problem and give me power up to ~7500rpm without losing down low where I am most of the time.
I THINK I'll be happy with mid-high 14's all-motor and 13's with a 50 shot of NOS.


[Modified by Muglit, 11:40 PM 12/3/2001]


[Modified by Muglit, 11:41 PM 12/3/2001]

 

Come on guys I know somebody has to have an idea. I'm losing at least 5hp(probably more) and some mpg so help me out


[Modified by Muglit, 8:30 AM 12/4/2001]

 

Get an S-AFC.

 

I thought about that but I lowered the FPR which lowers the fuel pressure across the board and no matter how low I went the top end was still running rich so that is why I think something is "wrong" not just in need of tuning.

 

Are you sure that your FPR is working correctly? The LS ECU normally runs the B20 a tad rich but nothing overly noticeable.

 

lowering fuel pressure doesn't control the pulse width that the ecu gives the injectors, like the other dude said get a safc. running rich has nothing to do with your header. it may be restrictive but its not the cause.

 

Thank for the suggestions so far.
Yes the FPR works because the fuel pressure gauge shows differing pressures and the dyno graph shows the curve leaner on the bottom end as lower the pressure.
Wouldn't the pulse widths that the ecu gives the injectors be determined by the stock LS program? if so why would it be making the top end so rich when:
1) It doesn't do this with other peoples setups
2) The ecu is for a smaller engine

The reason I thought it could be the header is because I thought it wasn't getting rid of the exhaust gasses and giving the sensor a false reading of rich when the combustion is just "dirty".

Is the Apexi unit the only one that would control the pulse width or would any unit like the hypertech shogun do the same?


[Modified by Muglit, 11:25 PM 12/4/2001]

 

Oooo wait wait wait...what year LS ECU is this? I mighthave something to show you

 

Hey...did your A/F look anything like my red plot?

 

It's a 95 OBD1

It looks kinda like that except the dip I see is later.

What did you do?


[Modified by Muglit, 11:36 PM 12/4/2001]


[Modified by Muglit, 11:38 PM 12/4/2001]

 

When Iswitched from my OBDII LS ecu to a OBDI ecu...it was WAY rich in the top end..look at the graph! The S-AFC fixed that in a hurry and you can see the gains

 

By george I think he's got it.

Thanks, the plots look real similar. So I guess I need a fuel computer.

I want to get the hypertech shogun unit so I can change fuel, timing, and rev limit from the cockpit, has anybody used it?

PS: Does anybody have an idea why the OBD1 ecu runs so rich?


[Modified by Muglit, 11:44 PM 12/4/2001]

 

The Shogun is nice from what Ive heard...BUT...

You have to do alot of tuning! Unlike the S-AFC hwere it starts at '0" and you add/subtract where you want fuel, the Shogun comes with a blank "map" and you have to tune it on the tune to even get it to make the same power as stock.

 

Are you sure?
I was just looking at the shogun online and the description says you can just hook it up to your ecu and adjust the fuel by +/- 2% and ignition by +/- 1 degree