I'm about to start the process of tuning my car for the highest boost possible, but I'm not sure what that is. I need a few opinions on what I can run, and what boost levels you run with your mods.

I have a built bottom end with 8.6:1 compression, 415cc injectors, and an Apexi S-AFC. My weak links are the Cartech FPR and no timing retard. My Cartech FPR works *most* of the time, but sometimes it will fluctuate. At 12psi of boost, I saw about 21 degrees of timing at 6000rpm.

Now, I know I don't have the BEST setup right now because of the FPR and no ignition, but I don't think it's too bad either. So how much higher can I go? Can I gradually turn up the boost until my timing reaches a certain point as long as my o2's don't go too lean and my EGT's are safe?

Thanks!

Patrick

hey bro, i dont got a built bottom end but i got everything else. 1st really get rid of a fpr, that cant hold stable fuel pressure! really unsafe if you ask me, i got a super fmu and it works great. i would say atleast change the fpr to a better unit like super-fmu and i would say to be safe 12-15psi till you need the ignition to retard timing. all cars sorta vary depending when they need some 'retard' people say 15psi+ but sometimes its a bit lower/higher. if you want to do 15psi+ get a ignition and 93 octane and you should be cool 1-2psi more. remember just because your running rich, does not mean its not detoxing.


Michael 99gs
HRC Stage 2
Stage 3 process begins anyone got a 420a block thats not spun/head for sale?

http://www.dreamwater.net/purplebeast

I was running 15 psi with no timing retard for a couple weeks and then it melted pistons. I was running .94-.96 when i datalogged it so I know I had enough fuel. Some cars can handle it and some cant. I wouldnt run over 12 psi without timing retard.

Retard :-)

Retard option is good of course but you may not need any at 15psi. Your data logging it right? I try and keep mine at 22-23 deg. at WOT.

If you are only getting 20-23deg advance at WOT I would say your good. One thing you guys are overlooking is the milti spark that the ignitions have. It is definitely needed at high boost levels.

Get a new "reliable" FPR and an ignition and your good to go 15-16psi all day long.

Brian

so erm when do you really need that ignition? Doesn't the computer sense knock and start pullin timing already?

Dave, are you sure it was your timing that melted your pistons? I thought you said your timing looked good when you datalogged it. See, here's my problem.....everyone says you need to retard timing for higher boost. But lets say I set the boost to 18psi and my timing is 23 degrees at WOT. Would I still need to retard timing, or is everyone SURE that I would see more timing at that boost level?

Then there's the issue of added spark with an ignition. I know that the 4g63 guys run 11 second 1/4 miles with their stock ignition. Don't we have the same one? Someone correct me if I'm wrong here.

I know I need a better FPR, but I refuse to believe that the only good FPR for our cars is the $300 S-FMU. Does anyone run anything else?

Patrick

P.S. - I only run 93 octane gas. Doesn't everyone??

You can get a 1:1 reg for like $130. But after playing w/ Corbin's fuel page for a couple hours I can say that you'd have to run stock static pressure in order to have enough fuel pressure under boost. If you lower your static way down to get a good idle then you won't have near enough fuel under boost. That's what I saw when I figured it. But I could be wrong.

And Dave's pistons melted because timing was advanced too much. Not in the upper RPM which is where he looked first but when he started to build boost at like 2-3K he had too much advance. Again correct me if I'm wrong.

>You can get a 1:1 reg for like $130. But after playing w/
>Corbin's fuel page for a couple hours I can say that you'd
>have to run stock static pressure in order to have enough
>fuel pressure under boost. If you lower your static way
>down to get a good idle then you won't have near enough fuel
>under boost. That's what I saw when I figured it. But I
>could be wrong.
>
>And Dave's pistons melted because timing was advanced too
>much. Not in the upper RPM which is where he looked first
>but when he started to build boost at like 2-3K he had too
>much advance. Again correct me if I'm wrong.

Okay, I guess that makes sense about the fuel pressures. But why can't I run stock static pressure so my boosted fuel pressure is okay, and use the S-AFC to lean it out for idle??

And about the timing issue. How did the fact that he was running higher boost have any effect on his timing at 2-3K rpms?? If he was just starting to build boost, it doesn't matter if he's running 5psi or 50psi, the ECU is still seeing only a couple psi of boost at that low rpm.

>>>Okay, I guess that makes sense about the fuel pressures. But why can't I run stock static pressure so my boosted fuel pressure is okay, and use the S-AFC to lean it out for idle??<<<

Hey my bad. I had that part in there but I was editing and forgot to put it back in. So yeah you can do that.


About Dave...IMO it's because of the AFC messing w/ the fuel trims in the low RPM and making the timing advance too much. In that case then you're right it wouldn't matter how much boost he was running. Armond had a good post on ASOG that explains his opinion. Let me find it....Ok here. Read Armond's reply in this topic. It makes perfect sense.

http://bbs.asog.net/viewtopic.php?t=29383

From what Armond said, anytime you use the AFC to lean out the mixture, the computer adds timing because it sees 100% manifold pressure all the time from the Missing Link. So for me to run my car like the one discussed on the ASOG board, I need to set my idle fuel pressure to 42psi and zero all my AFC settings.

I'm not sure how my car will idle yet, so I'll try it and see. If I get a rough idle, I can pull some fuel out of the 1000rpm range without having to worry about it affecting timing. But then how do I tune the car?? I was originally tuning by watching the STFT and LTFT, trying to bring them as close to zero as possible. But when I did that, I was taking out anywhere from 15-20% fuel in the curve at cruising and WOT conditions, and according to Armond that will create excessive timing.

And would I HAVE to use the Vortech S-FMU to set the car up this way, meaning using the car's ECU to mainly adjust fuel trims and timing, instead of using a 1:1 FPR??

Murix uses the 1:1 regulator. He can get away w/ using lower idle pressure because he uses bigger injectors so the 1:1 ratio is enough. I guess if you run it like that then you'll have to take what the ECU gives you. I haven't seen any datalog sheets w/ those setups so I don't know what the trims look like.

to your octane deal.. i live in so cal so i only get crappy 91octane at $1.75gal. unless i go put 100 octane in for 4.25gal...hehe


Michael 99gs
HRC Stage 2
Stage 3 process begins anyone got a 420a block thats not spun/head for sale?

http://www.dreamwater.net/purplebeast

$1.75 for 91 octane gas?? Wow, that sucks!! I thought I had it bad because there's only one gas station in the city of Colorado Springs that has a 93 octane pump. The guys up in Denver have 93 octane on just about every corner, lucky bastards!

Okay, so I'm still trying to figure this out....I still don't understand the timing issue. How does higher timing advance become dangerous at low rpms? My roommate has a 4g63 and I've watched her timing when she's datalogging. When she first shifts, she sees a lot of timing advance (30+) in lower rpms, but it immediately drops and slowly rises back to about 22 degrees by redline. So if Dave's car was doing the same thing, how did this damage his engine?

I'm also still confused on the FPR thing. I would much rather use a 1:1 FPR over the S-FMU because of price. So if I use a base fuel pressure of 50psi, and run 15psi of boost, my boosted fuel pressure would be 65psi. Would this supply enough fuel?

>>So if I use a base fuel pressure of 50psi, and run 15psi of boost, my boosted fuel pressure would be 65psi. Would this supply enough fuel?<<

No, not w/ 415cc injectors. Assuming you'll be making 300HP at 15psi you'll need 75psi fuel pressure. So if you use the 1:1 reg and set static to 60psi the you'll have enough pressure to run 15psi but you'll be grossly rich at idle. You'll have to lean it out a lot w/ the AFC. I wouldn't do that personally though. (read Corbin's post here: http://forums.2gnt.com/dcforum/DCForumID16/5055.html) If you want to get "decent" fuel trims them I'd say you're going to have to get the SFMU so you can run low idle pressures and have a rise rate so you'll have enough fuel under boost.