A/F values at WOT ?

[hondaNickx]

I recently installed a innovate MTX-L wideband sensor and have been watching my A/F values for some time now.
I changed my 4-2-1 header with cat for a modified Dc-sports 4-1 header with cat converter .
A/F values at WOT from ~ 5000 -7000rpm where before 13.5 up to 13.0 ,now with the 4-1 header it has gone up to 14.0 . Will this be a good gain in hp or is it not even noticable ?I'm going to get anonther dyno tune anyway but i was wondering if this change is worth some hp ?I notice the 4-1 header pulls better in higher revs then the 4-2-1 header before.

[saxophonias]

How is it in mid and low revs? What did you do with the relocation of the lamda sensor?

[hondaNickx]

How is it in mid and low revs? What did you do with the relocation of the lamda sensor?

Mid range revs it varies , around 12.9 to 14.I really need to hook up my laptop and start logging the A/F .

I installed a 2nd lambda bung a little bit before the original sensor location.So i have 2 sensors around de same location.
Just make sure they are not in line with each other ,they need to be offset so it doesn't effect flow around the sensor.

Best power is A/F 13.2 :1 afaik ? Right now it runs a bit lean into 14 :1 A/F , i'm going to get a retune anyway but i like to use the sensor to see what gains hp and what not.If it runs leaner then i asume the engine gets more air so the modification works.
I only know a little about tuning the A/F values ,maybe Joris can chime in here ?I know he know's more about this then me.

[hondaNickx]

I also have been testing different intake tubes to see if the A/F values would change.
-2.5" intake pipe with velocity stack /Nothing changed.
-3" intake pipe with oem airbox /Nothing changed.
-2.75" intake pipe with velocity stack/In high rpm A/F went up from 14 :1 to 14.5 :1 .This intake was also the longest of them all .(Comes against the headlight)And all intakes are short ram.

2.75" diameter seems to work best with a stock throttle body .That makes sence if you follow the statement of Endyn 25% larger area then the throttle body diameter = 69mm Inside diameter .The pipe i used has 70mm Inside diameter.

I haven't really looked into mid rpm A/F values since my engine always peaks hp on the rev limiter. (Around 7000rpm)
A/F values around 3500rpm are also around 14.5 - 15 but go down around 4500rpm to 13.5 - 14.

I will test a 3 inch intake pipe with velocity stack soon to see if that makes a difference vs the oem airbox.
If not then i will stick to the 2.75" intake pipe and make a proper one out of aluminium pipe with isolation.Intake length is another thing i like to test but i always asumed as close as possible to the headlight will work best .Since most ideal intake lengths for honda engines come out right in the headlight.

[saxophonias]

Useful info!!
Have you been testing open air filters too? I would like your opinion on the stock airbox too (ek3/4/9 style)

Just to mention that as for me after swapping a dc2 exhaust box I saw difference. I noticed gains in low and mid revs (from 1500rpms there is noticeable pull increase_4rth gear pulls from 40km easily_). Still I think I had some loss in high revs.

[hondaNickx]

Tested the 3inch intake didn't really get any better results.
2.75" seems to be the best ,at least on my engine.I actually used a OEM Prelude 97' intake tube .
They also use a 55mm throttle body like most D-series but the intake tube is longer and has a 70mm inside diameter.
The connection on the filter side steps up in size to 3inch .Which works perfect with my 3inch velocity stack.Intake length is about 500mm .
Anybody have any comments on the A/F ratios ?

[Dodo Bizar]

Hey Nick, thnx for the heads up PM. Sorry I've been reading so little around here, but sending a PM is defintively the way to get me reading (may there be some other topic somewhere, let me know).

First of all you are heading in the right direction Nick. From my experience with the B16B and some 3liter V6 Alfa, the longer runners always get you more power, so I expect your 4-1 to do the same, and yes the higher AF is a good indication that the engine has more air to burn now and hence can produce more power (and already will be producing more compared to the 4-2-1). I think that the AF of 14.1-14.5 is actually a bit scary, please get it as fast as possible between 12.5 and 13.5. We always tend to go to 12.5 on the higher revs, the power gains are almost the same as with 13.5, though the 12.5 keeps things cooler and safer. So definitely promising results.

Now for the intake length, I also believe the longer tubes are better and that the diameter will not change much. It has to do with the acoustic pulsation length which due to the relative low Mach number inside the intake tube is not altered much by either the 2.5, 2.75 or 3.0 inchers. Just the correct length is most important. Why you need the longest length or which length would be theoretical best if the headlight was not a limiting factor, I don't know. Typically the longer intakes work fine and the shorter ones are the worst.

[hondaNickx]

Hey Nick, thnx for the heads up PM. Sorry I've been reading so little around here, but sending a PM is defintively the way to get me reading (may there be some other topic somewhere, let me know).

First of all you are heading in the right direction Nick. From my experience with the B16B and some 3liter V6 Alfa, the longer runners always get you more power, so I expect your 4-1 to do the same, and yes the higher AF is a good indication that the engine has more air to burn now and hence can produce more power (and already will be producing more compared to the 4-2-1). I think that the AF of 14.1-14.5 is actually a bit scary, please get it as fast as possible between 12.5 and 13.5. We always tend to go to 12.5 on the higher revs, the power gains are almost the same as with 13.5, though the 12.5 keeps things cooler and safer. So definitely promising results.

Now for the intake length, I also believe the longer tubes are better and that the diameter will not change much. It has to do with the acoustic pulsation length which due to the relative low Mach number inside the intake tube is not altered much by either the 2.5, 2.75 or 3.0 inchers. Just the correct length is most important. Why you need the longest length or which length would be theoretical best if the headlight was not a limiting factor, I don't know. Typically the longer intakes work fine and the shorter ones are the worst.

Thanks Joris !
I'm doing a lot of testing on my ej9 lately so that's why i was wondering what safe A/F values would be.
I asked around and most said 14 :1 is still safe .I only rev the engine in that 14 /14.5 :1 area for testing a different intake.All the rest of the driving is under lambda control.I still have to test a few things after that i'm getting it tuned again.If i could adjust the A/F myself i would do it ,but i need to buy a lot of things (rom burner ,neptune ,etc )
Do you have any idea how much hp you would gain if you corrected the A/F from 14.5 to 12.5 or 13 on a D14 ?
Is it more like 2-3 hp or more like 7-8hp ?

[Dodo Bizar]

It's the latter... there is a lot to gain, especially when ignition timing is involved as well. It still depends, but with some setups I've seen over 10 hp after proper ECU tuning.

[saxophonias]

Back in the days when we were tuning my vafc (only a/f values) we would set it between 12.8 to 13.2 or something like that.
After tuning the vafc on the dyno we measured 7whp of difference in a dynapack. So yes there is room for gains.