View Full Version : attn van or 2g mas users, 2g maf tech Q's
I have a few results, I need to drop knock and advance timing.
any suggestions would be greatly appreciated!
I have now rid myself of fuel cut!!! what a relief, I used to hit fuel cut on a regular basis and was unable to take it above 5000 rpm's
I used a full 2nd gen intake setup,
2g intake pipe
2g mas
2g k&n fipk kit
the only thing this instal required me to buy was a slightly larger inside diameter bov-intake tube.
we datalogged a couple runs in 3rd gear starting at 3k rpm:
02 voltage- 9- 9.2 across
knock- 30 counts at over 5k rpm
inj pulse width- 17.6 @ wot
timing in single digits- 7-9 degrees
this run was done at 16 psi
safc settings-
5500rpm up is at +30%
graduating up from +15% @ 3500rpm
also karman readings with new mas in 3rd gear are only reading
1800hz.
with the 1st gen mas I was hitting 2075hz
I have the 2nd gen mas in my 92 tsi and I believe that you are still getting more air than what it reads. You see. The reason I decided to use the 2nd gen mas (as far as i understood it) it was to allow not less, but more air flow. However, you do not want the ECU to reconize this and cause it to throw a red flag and shut off the fun (i.e. "Fuel Cut") If we can run more air then we need more fuel as well, right? If you don't, then you can run lean and detonate.
You might have other issues to address but at least you've acomplished more air. Now you might need more fuel. And sometimes just turning up that AFC will not alwase do the trick. A good level of fuel flow can help to allow the type (or level) of fuel you need for more power with less knock. ... Knock sensors can go bad too. But if you don't have a bigger.. Fuel pump, lines, injectors, etc. then you'ld might want to start there. If you do, then, heat is your enemy and you can do several things to reduce that too.
Putting in the 2g MAS and NOT putting in 550's is NOT going to get you the results you wanted.
The two are a pretty good match.
The MAS reads less air, and the larger injectors put in almost the correct amount of fuel.
By doing MAS only, you use the AFC to bump UP the reported air flow.
Because the response is non-linear, you can't make it a fixed % based on rpms.
The ECU is seeing somewhat lower air flow numbers, so you get more advance... which means more knock.
Hal
Originally posted by Hal
The ECU is seeing somewhat lower air flow numbers, so you get more advance... which means more knock.
Hal My timing is at a horrible 7-9 degrees. I need to datalog it again, is it true that my ecu might adjust itself to the new mas and start advancing the timing back?
Is the timing being retarded a direct response from the ecu seeing knock?
Originally posted by Ryan
My timing is at a horrible 7-9 degrees. I need to datalog it again, is it true that my ecu might adjust itself to the new mas and start advancing the timing back?
Is the timing being retarded a direct response from the ecu seeing knock?
No, it won't adjust.
Timing is based on (for the most part) air flow.
Yes, the retard is due to knock
The 2G mas basically allows more airflow for the same Hz count. You demonstrated this and you are knocking like crazy at >5k because you haven't upped the fuel to match, or at least keep the knock sums semi-reasonable.
You list an IPW of 17.6ms @ wot, but it's at what rpm this 17.6ms occurs is what's important. ie: 17.6ms at 6500rpm is 95% DC., while 17.6ms at 5500 rpm is about 82% DC.
Also you post these three details:
5500rpm up is at +30%
02 voltage- 9- 9.2 across
knock- 30 counts at over 5k rpm
At first glance, these tell you that you don't have enough fuel and technically you don't. I ran the 2g mas with the stock 450's for awhile and never had to run +30%, but I had a walbro 255 already installed; so IMHO, that +30% datapoint says you are covering up heat with fuel. Not good. Given your current set-up and the details you've posted, I think it says turn down the boost until you can keep your max knock sums down around 10-11 counts or so. (That'll probably vary with daytime temps.) This should yield the most out of what you got for now. Then get some 550's and a bigger fuel pump asap.
Hey, Thanks alot for the info guys!:)
I guess I've maxed the stock 450's.
Im going to put in a walbro 255 in the next couple weeks.
By increasing the available fuel with a larger pump is it going to make much of a difference even though the 450's are hitting 95%?
the setup Im running is
jdm motor, mbc, 16g, 2.5 mand turbo back w test pipe and 2g ex manifold, 2g mas, act 2600, safc.
I think I will have to save some doe for 550's.
Originally posted by Ryan
I guess I've maxed the stock 450's.
By increasing the available fuel with a larger pump is it going to make much of a difference even though the 450's are hitting 95%?
the setup Im running is 16g
I didn't know you had a 16g, hehe. The pump will help at higher boost levels where the stock pump starts to drop in flow at the higher pressure.
That 16G is the cause of your +30% settings, vs. what I was seeing when I had the 2g mas and stock injectors on the 14b, doh!
I'd do the pump and the 550's asap.
Originally posted by Van
I didn't know you had a 16g, hehe. The pump will help at higher boost levels where the stock pump starts to drop in flow at the higher pressure.
That 16G is the cause of your +30% settings, vs. what I was seeing when I had the 2g mas and stock injectors on the 14b, doh!
I'd do the pump and the 550's asap.
thats where Im going... 550's a walbro 255 and as soon as I get rid of the knock... more boost!
V8SpankR
05-30-2002, 12:02 AM
If Ryan has those problems then how am I getting away with an 18g with stock injectors/pump @16psi on the 1st gen MAF with minimal probs? Am I lucky?
On 3rd gear highway pulls I see a max of about 8 counts of knock and 17 degrees advance above 6k rpm. My strip runs when the engine/IC has been cooled down net me zero knock til 4th gear and then I see 2-4 counts of knock and 20-23 degrees of advance and the car pulls nicely all the way.
What are good Karmen readings on a 1st gen MAF? With the DejonTool intake I am seeing just over 2330hz.
Perhaps there is another bottleneck in the fuel delivery system. Are the injectors dirty? Is the fuel filter dirty? Is there a kink in the fuel line? Is the in-tank 'sock' filter plugged up?
Originally posted by john
Perhaps there is another bottleneck in the fuel delivery system. Are the injectors dirty? Is the fuel filter dirty? Is there a kink in the fuel line? Is the in-tank 'sock' filter plugged up?
good point made John, I would like to have my entire system worked and upgraded. starting with the fuel pump.
Remember... by design... the 2g MAF (for the same volume of air) reports a LOWER hz.
That is why adding 550's "balances" out the air/fuel curve (to a large degree).
According to Todd, the increased flow of the 550's (w/o AFC compensation) matches the increase in "unmeasured" air flow.
The 1g ecu expects to see a higher hz number for a given volume of air. The 2g MAF reports a lower number, so you have what I will called "unmeasured" airflow. This air flow is very close (in volume %) to the difference in fuel flow between the 450 and 550 cc injectors.
Hal
Originally posted by Hal
Remember... by design... the 2g MAF (for the same volume of air) reports a LOWER hz.
That is why adding 550's "balances" out the air/fuel curve (to a large degree).
According to Todd, the increased flow of the 550's (w/o AFC compensation) matches the increase in "unmeasured" air flow.
The 1g ecu expects to see a higher hz number for a given volume of air. The 2g MAF reports a lower number, so you have what I will called "unmeasured" airflow. This air flow is very close (in volume %) to the difference in fuel flow between the 450 and 550 cc injectors.
Hal so according to this once I get a fuel pump and 550's my safc setting should basically be 0%?
If not zero, then close to what it would be for a 1g MAF/450cc combination.
Hal
With a 16g, you'll be in the + settings for WOT, at least on pump gas.
With the 2g mas, a 3" intake, the 14b ported, stock 450's and the 255lph; my s-afc settings were never "zero." Not even for the Lo settings, but Hal is right about what you'd see for a decently tuned 1g mas/450 combo.
The s-afc settings won't be linear with the % larger that stuff is, but will be relatively close though.
Don't be surprised if the walbro 255 rasises your base fp some and you have to account for it with the s-afc. That's the way mine was.
John brings up a good point about your fuel system! When was your fuel filter last changed?
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