Guys,

Ptatohed and I finished installing my new 99 SC kit on my 99 Max SE 5spd (CA spec) last night. We went really slow over the past week to ensure an awesome install. We double and triple checked all connections, hoses etc. We take it out for a spin last night and we cruise for 10 minutes just to let the car get used to the SC. All is well, the car is driving totally normal and not making any unusual noises. (except for those lovely crickets under the hood!) After 10 minutes, we decide it's time to get on it a little bit. At medium throttle, there is hesitation and "studdering" if you will. I backed off and never punched it. The car does not pull, and I felt no boost. We cruised for 10 more minutes and tried to give it medium throttle several times. Same thing happened--hesitation and that studdering feel.

We go home and scratch our heads on what it could be. Well, it's either fuel, spark, or air. We double check all connections again and rule out the possibility of air leak. Next, we think it fuel related. When I turn my key to the "on" position, I can hear the fuel pump kick on very faintly. On Ptatohed's car, when he puts his key to the "on" position, you can hear his fuel pump kick on LOUDLY, and hear the gas being pumped, even with the windows up from inside the car. Hmmm.... is this a clue we think? Not sure, we move on and decide to come back to this as it's a shot in the dark.

Next, we go for the spark plugs. First, let me state that before I threw on the SC, I did all maintenance to the Max except for spark plugs and air filter. I planned on changing the spark plugs w/in a few days of the SC install and the air filter is changed by default. I changed the coolant, fuel filter, PVC valve, and gear oil. We were hoping to find some really fouled spark plugs with huge gaps. Instead, we found normal wear and tear spark plugs (the proper NGK platinums) gapped anywhere from .39 to .44. (Spec is 0.43) We drop in new factory NGK plats gapped exactly to 0.40. It's 2am, so we called it a night and didn't test drive it.

This morning, on the way to work, I decide to get on it a little bit and see if my problem has changed. Well, the hesitation issue is not as bad as it was. Now, only at full throttle do I feel that hesitation. Boost seems to be there, but not very strong. I expected a serious kick in the pants feel, you know? I'm adding approximately 100 HP here.

So, am I on the right track with the spark plugs? or am I barking up the wrong tree? I'm thinking I should gap them down to 0.37 and see what happens. What gap do you recommend considering my situation?

BTW, here are my mods, just so you know exactly what we're dealing with here.

Cattman y-pipe
Cattman Fastcat
Stillen catback
3.25 pulley
I'm also using Amsoil 10w-30 synthetic oil

Thanks for taking the time to read all this and respond.

James

 

Did you do any checks on fuel pressure? If your fuel pressure isn't rising with boost pressure, then you will run lean.

If you don't have an in-cabin fuel pressure gauge, then get one ASAP.

An easy way to verify that your fmu is working (resulting in FP increase) is to monitor fuel pressure at idle while applying air pressure to the hose going to the fmu. You can do that with a Mityvac.

 

james,
get josh and bring your car down so we can check it out if u want...we can check all the readings.....and kick. I chatted with Josh earlier in the week (pm). U guys can roll down to west covina and some of us can check it out. good luck on the S/C progress...

 

The symptoms you describe sound like a coilpack problem to me. Under easy throttle my car behaved normally, but under more than 1/3 or 1/2 throttle, I got bucking and stuttering. The fact that new spark plugs helped the problem but didn't completely cure it makes it sound like a spark problem also.

 

check the hose to the stock fpr make sure its not crimped up and also recheck the three hoses attach to the vacuum tee. sounds like the fpr isnt seeing enough vaccum.

 

I would check belt tension too. do you have your gauges in? You can diagnose a lot from those.
Steve

 

Thanks for the replies. Much appreciated.

Ptatohed and I gapped them down to .037 and the car feels slightly better, but the hesitation is still there, but only under WOT. At medium throttle, there is no hesitation, but I still don't feel much power. I'm not getting the "pinned to the seat" feeling.

Stephen Max
No, we didn't do any checks on fuel pressure. We thought about it, and know we should check, but we don't have the tools or experience to do so. And I don't have any gauges yet. I planned on getting guages next, but I never thought I would need gauges to troubleshoot a SC install! Looks like I'll be getting gauges asap.

Does any company make a 2 guage pillar pod? I only see the 3 pod out there. So, I need a boost guage, a fuel pressure gauge, and "xxx" gauge ?

Maxlinegtr
Thank for the offer! I appreciate that. Sound like you have the tools and experience to troubleshoot my problem. Are you available next Friday afternoon, Saturday, or Sunday?

Nealoc187
I know 99's are famous for there coilpack problems, but my car felt great when it was NA. Would faulty coilpacks only rear their ugly heads now that I'm SC'd?

C MAX
Thanks for the idea. I checked, and everything is perfect.

Slimer
We've been checking the belt tension daily. Seems fine to us. We used the method of turning the belt 90 degrees between the crank pulley and AC pulley. That method kind of sucks though, because you can always push harder and get it past 90 degrees. We use moderate to heavy force, but not all of our might. At initial install, we used the deflection method and that came out good and coincided with the thumb/90 degree method.
No guages as of yet.


All
What different guages do I need? Any particular brand you guys lean towards? I'm kind of partial to Greddy guages, as I have the 60mm Greddy's in my Supra and I like them alot. Any reason not to go Greddy?

Overall, my hunch says it's fuel related. We'll see.

On a side note, the fuel pressure switch that Stilen provided me is completely different looking from Ptatohed's. Has there been issues with the switches over the years and Stillen gave me a better one? or did they just go with a different manufacturer over the years? Maybe I have a bad switch and it's not telling the pump to dump more fuel under WOT? Just guessing here.

James

 

ditch the hobbs switch and go with a afpr and a walbro combo. it will only set you back like $200 and you wont have to worry about it.

if you have a boost gauge, it will tell you if its slipping too.

as for gauges, anything works well, but electronic is better.

 

James,
Get rid of the Aux fuel pump and plop in the walbro fuel pump...its more reliable...it would ex-nay alot of wirings and such. check out all your fuel delivery components and FMU connection. I am so busy with other stuff I don't have enough time to do my swap. Good luck with the S/C.

 

I would rule out the Aux pump as the cause of your problems. It's more likely a coilpack like Neal said. When I had the SC, my aux pump wasn't working for a few months due to a crappy shop install (the power wire fell off) and it didn't give the symptoms you are describing. I could hit full boost, but the car just seemed down on power. No hesitation or stuttering. Bad spark would cause the problems you are describing though.

 

But, like I asked before, "I know 99's are famous for there coilpack problems, but my car felt great when it was NA. Would faulty coilpacks only rear their ugly heads now that I'm SC'd?"

Thanks for the input. I'll be checking on my coilpacks. I'll keep you guys updated.

James

 

I think mechanical is more than adequate for boost but fuel and oil should be done electronically. It really scares me that they even sell mechanicals of those types.

 

i have a mechanical fuel. you will see it saturday. its a cool little setup.

 

I read my FSM and Haynes and know how to check if my coilpacks are good. I'll be doing that tonight or tomorrow. Even if they check out good, I'll probably swap Ptatohed's coilpacks in and see if my problem goes away. I'll probably gap the plugs down to 0.034 as well. Oh, and I'll check the fuel pressure too.

Just a thought here.... The vacuum line Stillen provides weren't long enough for a clean install. I guess they assume a straight line between point A and point B. Anyway, I bought extra hose and chose my own route. The lines are probably about twice as long as they need to be if I was to go directly from point A to point B. So, can long vacuum lines be causing my problem?

James

 

I would ckeck your vacuum lines...your couplers and other related problems. go 1 section at a time. also check your piping if there is any leaks and looseness...check all the connection from fuel to air...also check your fuel and air ratio to see if u are running propperly. Good luck James.

 

the length of vacuum lines does not matter, but i used the silicone vacuum lines and it was tighter on the barbs.

 

Jim, I think your problem is that you insisted on using your (name brand) Craftsman tools instead of my (bargain brand) MasterCraft tools for the install.

 

I really doubt it is a coil pack problem. You said the car ran perfectly fine before the install....it is a possibility but I would check what you changed on the car, ie the SC. Fuel issue would be my first guess since it runs fine while not in boost. Since the FMU won't come into play untill boost that seems like a reasonable explanations. Like others said, your crazy not to run a FP gauge with an FMU. Your FMU is what is keeping you from blowing your motor and the FP gauge is what tells you that it is working.

 

Wiseguy....At least when YOU break my tools, I can go to Sears w/o a receipt and get a replacement, no questions asked. LOL



Thanks for your input Mike. I totally agree with you. I've checked, and rechecked everything again and again. My initial hunch says it's fuel too. Time to check that dreaded yellow wire going through the firewall… maybe it grounded out somehow. Then, maybe I’ll put Ptatohed’s FMU/Aux pump/hobb switch in and give that a try too. Oh, I just bought the Walbro 255lph hp fuel pump. Maybe I’ll drop him in and see if my problem goes away. As far as guages, I'm researching those as we speak.

Quick question about gauges.... If I'm boosting 10 psi, and the stock FMU disc is 8:1, then my fuel pressure is 10x8+(.5x34)=97 psi at WOT? ((34=stock fuel pressure) Am I correct? If so, then it appears I can't get Greddy fuel pressure gauge, because it only goes up to 6 kg/cm2, which is equivalent to 85 psi if I did my math right. Thoughts?

Thanks for all your advice guys.

 

Boost can have an effect on coilpacks. By adding boost the air in the chamber is more dense. It's harder for the coilpack to arc through the plug.

I noticed this on my 1.8t. They are notorious for bad coilpacks. While adjusting boost pressure, I noticed a slight misfire. I brought down the boost and it was gone. I replaced the packs and I'm back up to 18psi no problems.

Hope this helps.

 

Why .5x34?

 

Yes, your FP calculation is correct and that is really high fuel pressure to run. I am running 75-80 psi and I don't feel comfortable with it being that high. If you go walbro it will increase even more since the base fuel pressure will incrase about 7 or 8 psi. I would suggest, like I will be doing, getting away from running high fuel pressure with a ROM tune or larger injectors. it is just not a good idea to run like that.

As far as a fuel pressure gauge you gonna want something that reads at least 100 psi. There are not very many electric gauges that read that high of PSI, I know of the autometer and the defi. There are a couple other low end or off brand ones but I would not use those. I have the Defi FP gauge and like it alot. IThe fuel pressure sensor part is really small which makes for easier location and installation. It is about $170 IIRC from e-gauges.com

 

Broaner


I was reading an old fuel thread yesterday that Slimer sent me (Thanks Slimer!), and that's the formula that IceY2K1 used. I have no idea how it was derived. This stuff is all new to me.

Here's the link:

http://forums.maxima.org/showthread.php?t=288889


Mike,

What about putting in a 6:1 disc? That would drop the fuel pressure. Any bad side effects? Also, I could add an adjustable FPR to get me back down to OEM pressure with the addition of the Walbro? At least, that what I gathered from reading several threads yesterday.

First things first though, is to get the car running right before I start changing anything. That will keep the variables to a minimum. Guages should help tell the story....

James

 

to calculate fmu pressure, it starts out with hlaf the base fuel pressure.

so if you had the walbro and no afpr, you would take 42*.5 and calculate from there.

remember, your fpr is a rising rate at 1:1 as well. thats what the thread that james posted is calculating.
Steve

 

until you dyno with a wide band or data log with a wide band you won't know what disk is right for you. To small of a disk and you lean to large and your rich. Erroring on the rich, or larger disk, is the safe way. It is better to run a little higher fuel pressure and be richer than to run lower fuel pressure and be lean. With an 8:1 disk I was a 12:1 AF ratio at higher rpm's, a little lean for my tastes but had a lower fuel pressure of 65-70 psi. With the 10:1 disk I was rich at 10.5:1 - 10:1 but which gave me a higher 75-80 psi of fuel pressure. I chose to have a bit higher fuel pressure and run a safer AF which gives me some safety room for colder days where I might see 10-15 hp gain because of the weather or if I get .4 bar of boost instead of my usual .37-.38 bar.

So, run the larger disk until you know if you can go lower based on your AF ratios

 

mike i thought we messed around with only the 6 and the 8

 

8 and 10

my fuel pressure at peak boost is between 75-80 depending on what it peaks to, .36-.4 bar. Before the change in disks it was 65-70

(.5x42)+(5.5x8)= 65psi

(.5x42)+(5.5x10)= 76psi

 

But I thought the base had to be brought back down to ~34 with the Walbro; no?

Mike, 12:1 is lean? I thought that was conservative with boost.

 

No, the added base fuel pressure doesn't hurt anything. There are instances where you might want to turn it down though.

12:1 for a turbo car is pushing it. That is not to bad for a SC max though, you could get away with 12:1 on a SC max right up until maybe the last 500 rpm's. 11:1 is what I am aiming for.

 

Will I be able to run NA for a while without turning down the base?

 

yes. i ran on it for a couple of days this week.

 

you could run it forever like that

 

You'll be fine. Only time you need to turn down the fuel pressure is if you're running bigger injectors. Even w/ 370's, the car will start and idle fine at 42psi. Mileage just suffers some.

I have 660cc injectors, and the car started, idled, and ran fine at 42 psi. Mileage was really bad. And during some experimentation, I found that my car will still start and idle with 660's and 55 psi base.

It's now turned down to 26psi though. Seems to be the lowest that the car will idle at. I tried 24 psi and 22 psi, and the idle got rough, almost like the car was missing.

 

Wouldn't it be rich though? That is 23.5% more pressure than stock. I understand that the ECU can adjust on part throttle but at idle and WOT it will be rich; correct? Why am I not understanding this?

 

Fuel flow in a pipe is proportional to the square root of the pressure drop, so even though the pressure is 23% higher, the flow is only 11% more. That will make it richer, of course, but not as much as the pressure difference would make it seem, and apparently the engine will idle fine with that amount of enrichment. I also used to have my base fuel pressure set at 40 psi (with 370 cc/min injectors, but with the ecu tuned for them) and my engine was happy like that.

 

So I will be down on power for a while. I'll just hold off on installing it then. I got races to win.

 

The ECU will compensate at idle once it warms up. On startup, the engine is running off of the stock program and it will run rich, but once the engine warms up, the ECU adjusts. On the dyno, my car idled at 14:1 A/F, close enough to stoich.

 

think its FP here too...im not sure if its the case for 4th gens but on my 5th gen we had to get rid of a ground that was holding fuel pressure at the stock 60 psi (using a walbro 255 here)...after we finished that it buried the needle

 

PROBLEM SOLVED!

On Saturday, Josh and I swapped his 99 coilpacks into my car. What a difference! Holy torque steer Batman! We jumped on the freeway and I mashed it. Felt really good. I even had torque steer in the end of second gear. All hesitation and studdering is gone. Prior to the coil swap, I tested the coilpacks per the FSM, Haynes and Chiltons. Only Chilton gives an approximate reading of what to expect..0.8 ohms. The others just test for continuity. I passed the FSM test, passed 1 of 2 Hayne's tests, and failed the Chilton test.

After all is said and done, now Josh and I are wondering what other components "appear" to be working fine, but are really tired and worn out.
This is in reference to the fact that my car ran fine and quit a bit of power when I was NA. Although, when Josh and I raced each other NA style, we were pretty much even most of the time, and a few times he would pull on me ever so slightly. This didn't make sense to us since I'm stick, he's auto, I'm 60 lbs lighter than him (auto SE vs 5spd SE), I have a catback exhaust. We blamed it on my heavy, cheapo 18" rims that came with the car. That, and the fact that I have a few more miles than him, so maybe my car just needed a tune up.

Anyway, what other parts affect peformance beyond the scope of the typical tune-up?

Thanks to all for your help/suggestions. A big thanks goes to Neal, Shadow, and MadMax 95 for chiming in about the coilpacks. I never would have guessed that on my own. And finally, thanks to Ptatohed (Josh) for putting in countless hours over the last few weeks to help me install/troubleshoot my SC. Now it's time to finish putting his 96 back to NA and install his supercharger on his 99!

James

 

good to hear james. i'm glad it works now. enjoy the boost and make sure everything is running correctly.