Compensating for JWT's notoriously rich tunes...a neat trick

[MarkEmark]

So it's been a while since I gave an update about my KA-T in regards to what a/fs its been running.

With the larger turbo and fresh rebuild, the car felt amazing. I knew it was running rich, but not HOW rich. It felt plenty damn fast...I've been gradually increasing boost and am running around 13-14 psi right now (spikes to 15 or so, then levels off), and I doubt I'll increase it that much. I have an electronic exhaust cut-out that effectively eliminates half of the exhaust/muffler that allows an extra psi or so and even leaner A/F ratios if I'm feeling even more power-hungry.

Anyhow, I now have a Zeitronix ZT-2 A/F ratio monitor, along with the display and software, and have been able to data-log.



I was dismayed to find out just how rich the JWT's tunes are...Without adjusting anything, the A/Fs were about 10.0:1 WOT in 2nd, 3rd, and 4th gear. Clearly some power could be made from that.

I have an adjustable Aeromotive FPR, and bumped the fuel pressure down about 5 psi to 29 psi, but the a/fs were still very rich (10.3:1 or so). Click and drag the graph to a new window to see a larger picture...



I knew I couldn't just keep bumping the fuel pressure down without adversely affecting the injector spray pattern, so I came up with a clever solution. Before Enthalpy and AEM EMS even existed, for those of you who were still KA-T, you will remember not much existed for engine management. Hacked MAFS (a la Orion) were the hot-topic among do-it-yourself tuners. So I basically worked backwards from the hacked MAFS idea.

I already had a 5/8" nipple welded to my turbo inlet pipe where a hose from the PCV (on the valve cover) was attached. This nipple was AFTER my Cobra MAFS. So what I did was simply put a breather filter on that PCV system from the valve cover, and then attached a 5/8" vacuum hose with a breather filter to this nipple on the turbo inlet, meaning a steady stream of 5/8" air would be entering the turbo inlet, WITHOUT being metered by the MAFS, meaning it should, in theory, create a leaner condition. It worked, and without any detrimental side-effects, and made the A/Fs noticeably (by seat-of-the-pants and by data-logging) leaner.

I also already had a 1/4" nipple welded to the turbo inlet pipe a long while ago when I was first turbocharging the engine to bleed air from the wastegate line into the inlet to increase boost at the turbocharger. It used to be plugged because my new wastegate lets me run 14 psi without any tricking of the wastegate line. So I figured if a 5/8" stream of fresh, unmetered air made the a/fs leaner, then 1/4" more would make it even leaner, and it did. I used a panty-hose as a filter for this 1/4" line for an initial test, but will eventually somehow tie it into the other 5/8" hose (yeah, I've been critical of jury-rigging set-ups, and I'm guilty here, but it really does work and this was merely a test). So for those who are good at math, that means I now have a 7/8" stream of unmetered fresh air being introduced to the turbo past the MAFS.

Using these 2 breather lines, A/Fs were now a MUCH better 11.3:1 (at the richest, mostly it was around 11.5:1). When the exhaust cut-out on the downpipe is open, the mixture leans out even a little more to a very respectable 11.9:1 (partly due to the freer breathing engine, partly due to the 1 psi extra gained due to less back-pressure) in third gear at 6000+ rpm.



Here's some pics of the set-up:



Now that I know it works, I need to make it look a lot better and more permanent...I'm going to run the PCV line to a catch-can, and I need to find some way to tie the 1/4" nipple into the 5/8" one. I may just go ahead and re-do the turbo inlet pipe, welding a 1" pipe (instead of 7/8"...the extra 1/8" will make it a little leaner, but not too much leaner, and in any case, if it ever got too lean, I could always increase my fuel pressure...) to the pipe after the MAFS.

Anyhow, basically the purpose of the post is to show people that for those stuck with the super-rich JWT ECU and do not want to mess around with an S-AFC II (nor have the money to), there is still hope!!

[rlvq35de]

i plan on getting the JWT ecu. I figured I would use the apexi NEO i just picked up to trim out the A/F. Is that a better solution? Or are you just doing that as a temporary fix?

[S14tat]

very neat trick you got there. did you feel a very noticable increase in power from running in the power afr? the car must be a beast lol.

[PapaSmurf2k3]

Good writeup... too bad this wont work for blow-through MAF setups

[KATwo40]

hehe...

You said "nipple."

[pr240sx]

Great trick butHow does this "leak"affects idle quality?

Also, are those nude or taupe?

[AZhitman]

I'll be running JWT as well - Great info!!!

[MarkEmark]

i plan on getting the JWT ecu. I figured I would use the apexi NEO i just picked up to trim out the A/F. Is that a better solution? Or are you just doing that as a temporary fix?

I'm sure you have a lot more control over the A/F ratios with your apexi unit...although now that I think about it, both piggy-back fuel controllers and my method do the same thing: trick the ECU to manipulate the air/fuel ratio, just in different ways. I'm just saying that for me, the idea worked pretty well and leaned out the ratio enough to make the car feel substantially faster.

Yes, the car feels like a beast, especially with the exhaust cut-out open. I was doing some "open downpipe" tests yesterday night and my dad was out on the deck having a cigarette and heard me probably about 4-5 miles away...he even knew how many times I shifted! Said it sounded like a muscle car hah

pr240sx: surprisingly, the idle is PERFECT. Rock-solid at around 800 rpm. There's been NO negative drawbacks as far as drivability/vacuum goes. The car isn't more prone to stalling either. In fact, I haven't stalled the car ONCE since the new break-in...I can stop hard and put the clutch in and it won't stall, although this is partly due to my recirculated adjustable bypass valve and what spring tension it's running.

No idea what kind of panty-hose they are (whatever my mom wears ), although they seem to work darn well! Flows plenty but definitely filters out even diminutive particles.

I'm going to the dominican republic on saturday (Punta Cana) and will be gone for a week, but after that I'll re-do the intake piping and post pics, of course.

[Jookmasta]

my query with this was the idle but u answered that. good stuff. something like that just saved u the money u wouldve spent on an safc. i know the nipples cost nothing but how much was the exhaust cut out? just trying to give peeps an idea as to how much they would save if they decided to pursue your route.

also as a sidenote, i was looking over your zeitronix images that you posted and i suggest that when your doing ur pulls, the pedal is to the floor..............aka your tps is at 100. just makes that full throttle run a bit more accurate wouldnt you say? good stuff man.

[MarkEmark]

my query with this was the idle but u answered that. good stuff. something like that just saved u the money u wouldve spent on an safc. i know the nipples cost nothing but how much was the exhaust cut out? just trying to give peeps an idea as to how much they would save if they decided to pursue your route.

also as a sidenote, i was looking over your zeitronix images that you posted and i suggest that when your doing ur pulls, the pedal is to the floor..............aka your tps is at 100. just makes that full throttle run a bit more accurate wouldnt you say? good stuff man.

Exhaust cut-out was $189 from JEGS. Very well made, lifetime warantee...I also added a 90 degree turn down to divert the gases away from the underbody of the car.

Ignore the EGT, TPS and Boost readings on the zeitronix...none of that is set-up.

BELIEVE ME, I was full throttle on those runs!! You can't tell from the chart I posted, but on the file I have, you can see how fast the acceleration is by seeing how many seconds it takes to get from 2nd gear at like 3k to 4th gear at 5600....it's about 8 seconds.

[pr240sx]

Bring some PRESIDENTE from Punta Cana!!!That place rocks!!Hope that you are going to an all inclusive hotel.

[MarkEmark]

Bring some PRESIDENTE from Punta Cana!!!That place rocks!!Hope that you are going to an all inclusive hotel.

Hah, yeah it's an all-inclusive resort, should be a sweet time. The complimentary alcohol makes it worthwhile, as does the under-21 drinking age

Lookin' forward to utilizing some of my spanish-speaking skillz haha.

[Structure240sx]

this was brought up a while back when WD was discussing the hacked mafs idea with bigger piping and/or using a 2nd filter after the mafs like you are suggesting

one point that could be brought up but is not too significant, is that if the 2nd filter becomes dirty over time it can restrict the new flow. thus making u get richer. not a huge deal at all but something to keep in mind.

i have read about people running 550's on the stock ecu this way. basically having a y-pipe for an intake pipe. both pipes being the same size as the stock maf but one being open to lean out the 550's perfectly since 550's are twice the size of stock 270's. so twice as much air getting in for twice as much fuel. would be fun to try out

[BillKlineVT]

Only concern with this rather simple workaround is air temperature. You may want to check on how lean it gets in colder temps aka at night or when it gets colder out in the fall. It may not be a significant change, but it'd be worth knowing for peace of mind.

[C-Kwik]

Only concern with this rather simple workaround is air temperature. You may want to check on how lean it gets in colder temps aka at night or when it gets colder out in the fall. It may not be a significant change, but it'd be worth knowing for peace of mind.

Shouldn't have to worry about that. The MAF will pick up changes in the air density caused by temp changes automatically. Since the orafice is fixed, it should bleed in a proportional amount of air at all times.

Though, based on the entry angle, at high airflow rates, the air being bled in may become a lower proportion of the total airflow as the column of air in the main pipe would probably restrict some of the air being pulled in through the bypass tube. An angled entry will probably help. But this shouldn't be a dangerous situation as it would cause your engine to run richer(no richer than with the JWT tune) at worst.

[BillKlineVT]

Right, I know the MAF will, but it won't pick up on change in density of the unmetered air. The change in temp may not cause a linear change in how the MAF reads the airflow... probably not a huge concern though

Shouldn't have to worry about that. The MAF will pick up changes in the air density caused by temp changes automatically. Since the orafice is fixed, it should bleed in a proportional amount of air at all times.

[Structure240sx]

from what i have seen tunned ecu's at least jwt eliminates the IAT sensor. on my mdm techtom it no longer picks up a reading from it with the jwt ecu. also the afr's stay closely the same between cold and hot temps compared to using a stock ecu and piggback alone, would need adjustment from day to night if the temperature changes enough

[C-Kwik]

Only concern with this rather simple workaround is air temperature. You may want to check on how lean it gets in colder temps aka at night or when it gets colder out in the fall. It may not be a significant change, but it'd be worth knowing for peace of mind.

That's what I am saying...it DOES pick up on the change. The MAF works by heating a wire with voltage. As air goes across the wire, the air carries away heat. The ECU measures how much voltage is needed to maintain teh temperature of the hot wire. How much heat is carried away by the air is directly related to the flow of air and the density. The colder air will be more dense and more heat can transfer to the air quicker. Therefore the voltage the ECU has to send will be higher so the ECU will know more air is going to the motor. The MAF is designed to measure the mass of air. Plunger or trap door MAF's need to calculate air temperature as they only measure flow. Hot wire MAFs are quite accurate when they are set-up correctly. The air temp sensors in hot wire maf equipped cars are used for emissions. Other then getting a CEL light with it disconnected, I never had any issues in the way it ran without one(for the short period of time I had disconnected it...errr....forgot to plug it back in).

[BillKlineVT]

Right, I know the MAF will, but it won't pick up on change in density of the unmetered air. The change in temp may not cause a linear change in how the MAF reads the airflow... probably not a huge concern though

Did you read my last post? (quoted above). By "unmetered air" I meed the air from the tube inbetween the maf and turbo. I know how a hotwire maf works. I'll stop repeating myself because it's not worth the hassle... if it works it works, enough said.

[C-Kwik]

Yes, I did read your last post and you are missing the point entirely. I had emphasized a very key word for you to make it clear that I did. The air density, even in the unmetered tube is already compensated for. Unless the air for each tube is being picked up in completely different environments, then the density will be the same. Therefore the ECU does not need to know the temperature of the unmetered tube. Since the unmetered tube will be flowing a constant ratio (assuming it's designed correctly) to the amount of air that is being metered, it will always be the same percentage of the total air.

Look at this product:

http://www.stillen.com/product...03100

This is very similar to how the idea discussed in this thread works. One bank of cylinders will be metered, the other will not. The unmetered side will flow 50% of the total air being pulled in by the motor. It's not somehow magically pulling in denser cooler air than the other.

[BillKlineVT]

Okay, I guess that makes sense, for some reason I wasn't thinking there'd be a linear relationship with the change in density of the unmetered air and the ECU's fuel correction, thus requiring a varying "unmetered orifice" based on air temp. However, as you pointed out, the hotwire MAF should account for that change based on the metered air.

Also, I commend you on keeping your reply civil... I'm not trying to be a prick, I was just questioning the logic, seems clear now.

[veovius]

Uh, I'm not sure if you've realized this, but a 5/8" tube + a 1/4" tube does not equal a 7/8" tube. It may be close, but it's not the same.

pi*r^2 = area of tube

5/8" = 3.14*(2.5/8)^2 = 0.306641/4" = 3.14*(1/8)^2 = 0.04906Total = 0.3557

7/8" = 3.14*(3.5/8)^2 = 0.60101

So the 7/8" tube is almost twice as large as your two hoses combined. What you need to run is....

3.14*r^2 = 0.3557r^2 = 0.11328r = 0.33657

Diameter of hose is 2R ~= 0.673". So roughly an 11/16" hose, and that's a hair larger than what you've got right now

And before anyone else says it....NARRRRRR.

[MarkEmark]

Uh, I'm not sure if you've realized this, but a 5/8" tube + a 1/4" tube does not equal a 7/8" tube. It may be close, but it's not the same.

pi*r^2 = area of tube

5/8" = 3.14*(2.5/8)^2 = 0.306641/4" = 3.14*(1/8)^2 = 0.04906Total = 0.3557

7/8" = 3.14*(3.5/8)^2 = 0.60101

So the 7/8" tube is almost twice as large as your two hoses combined. What you need to run is....

3.14*r^2 = 0.3557r^2 = 0.11328r = 0.33657

Diameter of hose is 2R ~= 0.673". So roughly an 11/16" hose, and that's a hair larger than what you've got right now

And before anyone else says it....NARRRRRR.

Quite right, that was some stupid reasoning on my part. I'm going to go with a 3/4" OD pipe, which will have an area of around .44" versus the .35" and should be just enough to lean it out even a bit more (and again, I can always increase fuel pressure if too lean a situation were created by this).

As far as the angled-entry of the bypass tube, I was just planning on going with a 90 degree J bend because they don't make 45" bends in 3/4"....and I thought the whole concept of the venturi effect would cause the air in the bypass tube to be literally sucked into the main air-stream. I don't think the angle of entry will affect the basis of the idea that much, as it seems to be working fine right now with a 90 degree entry.

I'll keep ya posted...

and Pr240sx: you're right, presidente beer does rock! So much better than the crappy busch and bud-light I'm used to drinking!

[C-Kwik]

Also, I commend you on keeping your reply civil... I'm not trying to be a prick, I was just questioning the logic, seems clear now.

Thanks. I should say the same to you. It never ends well when you make a debate/discussion personal. If you stick to the facts everyone wins.

[volfan98]

couldn't you just plumb the entry side of your "bypass" back into the inlet pipe before the MAF? Basically just a hose that bypasses the MAF? That way you would only have to worry about one filter.

Matt

[MarkEmark]

couldn't you just plumb the entry side of your "bypass" back into the inlet pipe before the MAF? Basically just a hose that bypasses the MAF? That way you would only have to worry about one filter.

Matt

??? Not really sure what you're trying to say here, but the whole purpose of the bypass tube as you're calling it is to introduce air into the air-inlet stream AFTER the MAFS so it's unmetered and therefore causes a leaner condition...if the MAFS meters the air from the extra tube, the A/Fs stay the same....

[C-Kwik]

I think he's suggesting plumbing one end of the tube before the MAF and the other after it.

[MarkEmark]

I think he's suggesting plumbing one end of the tube before the MAF and the other after it.

I see, but I don't want to take air from the main stream to route past the MAFS; I want the bypass tube to take air from its own separate source.

I ordered 3/4" OD (.62" ID) stainless-steel tubing from http://www.burnsstainless.com (btw, great website, they sell everything from inconel to aluminum, and it's ALL in stock). I'll have that stuff here by Thursday and should have the new air-intake ready over the weekend. Then finally I'll be able to dyno the thing! I'm hoping for around 330 whp....

[MarkEmark]

UPDATE:

Got the parts in from burnsstainless (T-304 stainless steel) and had it all welded yesterday. Came out VERY nicely, and looks super-professional compared to the stupid hoses I was using before...

NICO photopost is down right now for some reason, so I'm using webshots to host...CLICK AND DRAG THE "IMAGE" Icon to a new window to see the pictures!



If you look closely in the picture, you will see a small K&N filter that drops into the fender well, right next to where the main air filter is (both cold air)



You can see how good of a job the welder did with the stainless in this pic...TIG, of course.



And a shot of the engine bay...finally got those two aluminum intercooler pipes welded together (instead of using a coupler and hose clamps) while I was getting the other stuff welded.



Now I need to do some data-logging. It's disgustingly hot and humid here right now, so I'll wait till night to do it, even though there's no real difference in the a/f ratio based on temperature (because the IAT sensor is apparently disabled by JWT tunes), one more reason I think MAP is far better than a MAFS system...

Modified by MarkEmark at 3:16 AM 6/21/2006
Modified by MarkEmark at 4:45 PM 6/22/2006