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Old 09-08-2011, 09:51 PM   #1
gallacmic
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The big 420a Mystery! Please Help!!!

Ok so I have a fully built 420a and recently finished the break in and is ready for now just 7 psi boost until funds are ready for a port fueler or megasquirt. So for now its forged internals, ported, 1mm oversized valves, ARP studs main and head. 60mm TB OBX ported intake mani, Stock injectors with a 255 hp walbro, 12:1 Vortech. Garrett T-3 Turbo. MSD coil. I have oil, boost, fuel, wideband a/f and volt gauges.
WHEW!!! So now to the issue. 2 issues actually.

Issue #1:
The turbo does not hit 7 psi. I did a boost leak test and I'm air tight! The boost starts building at 2k rpms and hits 4 psi at almost 4k rpms. I opened the wastegate lid to see if the plunger was stuck and its fine. I still do not have the BOV adjusted correctly and have compressor surge, so that cant be opening under boost I assume too. I installed a check valve going to the brake booster and one going to the evap canister. Every part on this car is brand new! Any ideas I could try??

Issue #2 :
At 4 psi boost the a/f gauge is saying I'm still in the 14 range which I know under boost is way lean. Should be 11-12 range. The most I pushed the car was to 4psi and then let off because of the a/f gauge reading. Dont want to blow the motor. The fuel gauge is only going up 20 psi with the 4 pounds of boost!! And it has a 12:1 disc!!!!! The static fuel pressure for stock injectors is 50 psi and at 4 psi boost the fuel pressure only hits 70. This is making me lean and I know I have no leeks going to the FMU. What else could be going on? I have an AFPR before the FMU that for kicks I cranked the idle pressure up to 100 to test the fuel pump to see if it could even go up that high and sure enough it does. So does this sound like a defective FMU or injectors? What am I missing here??
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Old 09-09-2011, 08:02 AM   #2
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Re: The big 420a Mystery! Please Help!!!

Sounds like a pretty awesome setup man! I'd love to see a thread of some pictures of it all... I'm a 4g63 guy so my knowledge on the 420a is limited but we have a few members here who have turbocharged their 420a motors and had some beastly setups. Hopefully they will be able to chime in and help out on this...

Based on your descriptions here would be my assumptions, and mind you I don't know the stock 420a specs so much, but it sounds like you might be pushing the injectors to their limits. Do you know what cc the factory ones are?

Also, what wastegate are you using? I know you can get different rated springs for them depending on how many psi you wanna run. Perhaps yours is a 4psi spring and your boost controller isn't functioning properly? I had this happen once with a bad controller and was unable to run more than 12psi bc it was defaulting to the wastegate spring rating.
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Old 09-09-2011, 09:28 AM   #3
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Re: The big 420a Mystery! Please Help!!!

Stock injectors are good up to about 12psi before you max them out.

Get rid of the FMU. If you have a built motor and looking for good, steady boost, dump that. At least teh AFPR is keeping the pressure low, but I would dump both and get a SFMU, with the adjustable static adjustment. Will be easier to adjust, and have less problems than with the FMU.

Not sure how big the turbo is, so can't say if 4psi @ 4k is a good range for it. I had a small T3 that was hitting about 7psi by 4k.

What happens past 4k? Does it just stop building boost?
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Old 09-09-2011, 01:12 PM   #4
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Re: The big 420a Mystery! Please Help!!!

Thank you for the quick replys! K so I have the JDM 38mm wastegate with a 7.2 psi spring in it. No boost controller yet installed because I'm not going to push the stock injectors past 7 psi. From what I have read on other forums 7-8 psi is max for the stockers. They are I believe 195cc and 19 lb/hr. according to vortech the 12:1 is specifically for 19lb/hr injectors. Now with getting a super FMU it still is a FMU with the same concept of raising boost with the disc and diaphragm as the standard right? Besides the fact that it can adjust static pressure? I hate how much they ask for those stupid things even the standard FMU was a rip! If I am maxing out the stock injectors do you know if the 420a can have larger injectors without adding a neo or some injector control module? Just kind of stuck with money for school and and least want to get 7 psi while I'm gone for spring semester. Hopefully get up to 17 psi down the road when money is better. As for the boost pressure at 4k rpms. I let off the gas and dont push it any further to see if it will hit 7 because the gauge is saying I'm lean so I dont chance it. On forums I have read that people build and hit 7 rather quickly by 4k. I beleive the exhaust wheel on my turbo is 50 and the intake is 60.
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Old 09-10-2011, 10:01 AM   #5
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Re: The big 420a Mystery! Please Help!!!

Dave and Jason are the best guys to talk to when it comes to 420a knowledge around here!

I guess my 4g63 knowledge just won't help much in this situation. lol

Good luck to ya and hope you guys can get it resolved!
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Old 09-10-2011, 10:47 AM   #6
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Re: The big 420a Mystery! Please Help!!!

Like Dave said the FMU is the absolute worst fuel setup on the planet for the 420a. Yea it half way works but I never had good luck with it. There are a few things I am seeing with your setup. What year is your car?

1) You say JDM wastegate... meaning ebay wastegate? A wastegate is something I would not go cheap on. They have issues failing under intense heat and not opening. Also if you have ~7psi spring in there by the time you get some pressure drop threw the intercooler and more than likely your boost gauge is a little off also. My autometer gauge reads almost 2psi off. I would put a bigger spring in the wastegate and see if that helps.

2) Most people do not run a AFPR with a FMU. They run the stock regulator. Im guessing you also have a vac/boost line going to the AFPR. Unless you have a 95 car the stock FPR does not change pressure at all. It always sits at 48psi. That means you should set your AFPR at 48psi static pressure and not run a vac line to it.

Now for your FMU issues. Do you have the Vortech FMU or some cheap ebay FMU. I would check the diagram put pulling a vac on it and see if its leaking or sealed. You can test it by just sucking on the other end of the hose. You could also check to make sure that the disk inside is in fact the right disc and they didn't tell you its a 12:1 when in fact its not. If it is one of the cheaper ones that could also be your problem.

It also depends on how you drive the car when you are messuring air/fuel. The stock ECU will stay in closed loop and try to keep a/f ratio close to stoichiometric until it goes into open loop mode. So when you go to test the a/f ratio again start around 2k rpms and floor the car this will kick the ECU into open loop and the a/f ratio should drop into the 13s. If your FMU still doesn't work correctly the car may still lean out with boost so be careful of that. However only 4psi and still on the stock ignition you wont cause any damage running a little lean a few times when sorting this thing out. I wouldnt go dog the shit out of the car though.
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Old 10-28-2011, 03:48 AM   #7
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Re: The big 420a Mystery! Please Help!!!

Ok so here is an update. I added some new accell 310cc injectors and was able to get the a/f ratio to go to 11.2 - 12.5 under boost but only if I floored it! When the throttle is not mashed down to the floor the car tries to keep the mixture at 14.7 Is this something to be concerned about? I know that 14.7 under boost technically is bad but I cant make it go to 12.5 unless its wide open throttle. I hope this does not mean I have to floor the car everywhere I go to keep the a/f mixture safe under boost! I made my own boost leak tester and made sure everything is sealed and its nice and air tight. The turbo seams to build boost kind of slow still but maybe its because the turbo is too big? Its a 50 trim on the exhaust side and 60 on the intake side. The wastegate is a jdm ebay one and my FMU is a 12:1 Vortech. I made sure it has the 12:1 disc in it too and ordered the calibration kit just in case I need to make some adjustments.
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Old 10-31-2011, 09:53 AM   #8
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Re: The big 420a Mystery! Please Help!!!

Quote:
Originally Posted by gallacmic View Post
Ok so here is an update. I added some new accell 310cc injectors and was able to get the a/f ratio to go to 11.2 - 12.5 under boost but only if I floored it! When the throttle is not mashed down to the floor the car tries to keep the mixture at 14.7 Is this something to be concerned about? I know that 14.7 under boost technically is bad but I cant make it go to 12.5 unless its wide open throttle. I hope this does not mean I have to floor the car everywhere I go to keep the a/f mixture safe under boost! I made my own boost leak tester and made sure everything is sealed and its nice and air tight. The turbo seams to build boost kind of slow still but maybe its because the turbo is too big? Its a 50 trim on the exhaust side and 60 on the intake side. The wastegate is a jdm ebay one and my FMU is a 12:1 Vortech. I made sure it has the 12:1 disc in it too and ordered the calibration kit just in case I need to make some adjustments.

The stock ECU tries to keep AF at 14.7 unless under WOT, which is why it's going rich when you floor it automatically. That's how it's supposed to work. TPS sends the position of the throttle to the ECU, and it adjusts the fuel to a

The motor won't need that much fuel if you're not at WOT. I'm sure you will have some lean spots on there at certain rpms/pressure points, but there's not a way to adjust those without a standalong/piggyback unit.
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Old 10-31-2011, 11:40 AM   #9
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Re: The big 420a Mystery! Please Help!!!

Well I got a completely different BOV and it opens right finally and damn I took the car out for its maiden voyage and it hauls ass for only 9 psi! Very happy with it! The weird thing now is that I had to chop the spring in the BOV way down to get it to open up right. There is amost no spring at all like the BOV operates completely on vacuum and boost pressure. EVEN still when I hit 6.5k rpms the turbo will have compressor surge for like a second. IS this one of the reasons people go with a dual BOV set up? It wouuld make sense that one BOV just isn't enough to let the pressure escape fast enough. As for the A/F mixture. I guess that as long as it being in the 13-14 range when it has some boost but not open throttle its ok. For sure WOT hits 11.8-12.5 so its good there. Thanks for all the reply's!
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Old 11-01-2011, 07:49 AM   #10
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Re: The big 420a Mystery! Please Help!!!

You're not running anywhere near enough boost to need a dual BOV setup. You should never cut a BOV spring. I didn't see anywhere on here listed what BOV you're using. I'm going to assume since you got an ebay wastegate, that you're using an ebay BOV. Most of those have a nut on the top that you tighten/loosen to where you need it so that it lets go of the pressure quick enough. I used a 1G BOV which are nonadjustable and it worked perfect.
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Old 11-01-2011, 09:44 AM   #11
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Re: The big 420a Mystery! Please Help!!!

Ok the problem you are seeing is when the ECU is switching to open/closed loop. Its goes directly into open loop when u stop on the gas and pours fuel in, going part throttle its stays in closed loop and tries to lean out the mixture. It should still kick into open loop once enough loads gets on the motor. Also you should not be running 310cc injectors with out an adjustable FPR
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Old 11-01-2011, 04:59 PM   #12
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Re: The big 420a Mystery! Please Help!!!

Ya that is weird! I put on the blow off valve and adjusted the screw to lthe lowest setting and it had compressor surge. So I opened it up and took out one of the 2 springs and did the test again on the lowest setting and still compressor surge. So I opened it up again and chopped the spring down to like an inch and a half long and it started working perfectly until I go over 6k rpms. I looked on another forum and read that in some cases you need to just go get a super soft spring from the hardware store to get it to operate correctly and it seems this might be what I need to do. Also I ordered an air filter that will fit over the blow off valve so during idle it will not suck in any dirt. Also I need to mention I do have an adjustable FPR for my 310cc injectors. I lowered the idle pressure to 45 psi and thats where it seems to run the best according to the a/f gauge. THE NEW PROBLEM NOW IS I DID A BOOST LEAK TEST AND THE DAMN THROTTLE BODY SHAFT SEAL IS LEEKING!!! This is a modern performance 60mm throttle body. Anyone know where to get the actual seal for that thing? I have never had good luck in the past just using universal o rings to fix the problem I still had boost leak.
THANK YOU SO MUCH TO EVERYONE THAT TAKES THE TIME TO HELP ME OUT!!!!!!!!!!!!
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Old 11-01-2011, 07:42 PM   #13
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Re: The big 420a Mystery! Please Help!!!

Some BOV sound like compressor surge when its really not. I have a hard time believing you are actually getting compressor surge if the BOV is fully functioning. Especially at only 8psi. I wouldn't worry much about it to be honest with you. Also I wouldn't worry about it sucking in air at idle. Mine actually blows out air at idle from the turbo spinning. You can also tighten the spring some to keep it closed at idle. Also stock fuel pressure is about 45-48psi unless u have a 95 then it is lower in vac. You need to lower your fuel pressure a little more to keep the fuel trims in check. I believe stock FI are 235cc

235/310 = 0.76 so you need to lower your fuel pressure by 76%.
0.76*45 = 34 So I would start around 34psi and work your way from there.

You really need to be able to read fuel trims on the stock ECU to get the injectors scaled right. The stock ECU can add or subtract 20%, so if you have the pressure raised to high the ECU will pull out up to 20% to keep the AFR around stoichiometric. This obviously works but now your fuel trims are maxed out and when the stock computer needs to pull more fuel it can no longer do so.
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Megasquirt 2 - Holset HY35 Turbo - Built motor - P&P Head and Intake - 3" Turbo back - FMIC - Greddy RZ BOV - Walbro 255 - Aeromotive AFPR - 650cc Injectors - Fidanza Flywheel - Zoom clutch - 13" Cobra Front Brakes - AEM WB - Devilsown meth injection - 3.55 Final Drive gear ratio

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1987 Nissan 300zx - Chump Car
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Old 11-02-2011, 12:45 AM   #14
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Re: The big 420a Mystery! Please Help!!!

Thats a way cool formula you have there for figuring out fuel pressures! I lowered mine to 30 and it semmed a tad too lean so I raised it up to forty and it seems good but 43 according to the formula seems like it would be perfect. For sure I know the BOV is sucking air in you can feel it with your hand. So the filter is on its way and that should take care of any risks with that thing. Most the time I'm not taking the car over 6k rpms so its not much of a problem. If I do the turbo makes a psh psh psh sound instead of the BOV making one smooth PSSSSSHHH sound. But I went and got a bunch of different springs to test I'm sure one of them will work!
Thanks again for all you shared knowledge!
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Old 11-02-2011, 12:53 AM   #15
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Re: The big 420a Mystery! Please Help!!!

Oh I forgot to add that I put in a 9 psi wastegate spring now That I have the 310's in and it hot 9 psi boost exactly! Nice and quick! Amazing what some extreme porting does!
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