JRSC Fuel Problems, UURRGGGHHHH - Honda Prelude Forum

luder621 · 02-07-2005, 08:22 AM

For those of you running bigger injectors, 550cc particularly, are you also using the fuel pump included with the JRSC kit? I had 550s put on and the shop closed the JR FMU all the way and it is still too much fuel. He tried using the VAFC also, but said it wasn't doing much. Just curious if I should be using the stock fuel pump with bigger injectors. Thanks.

sharkcohen · 02-07-2005, 10:43 AM

Well, you can't just install 550 cc injectors. First of all, the JR FMU has to come out entirely, you cannot try to 'close it all the way'. ALL of the JR stuff needs to come out, including the fuel pump. You should run on the stock pump. You need some sort of programmable management, such as Hondata, AEM EMS, EFI PMS, or Greddy E-manage. A VAFC will not be able to control 550 cc injectors.

Sounds like it's time for a new shop.

luder621 · 02-07-2005, 11:00 AM

What size will a VAFC be able to control??? 310cc? 370cc?

sharkcohen · 02-07-2005, 11:15 AM

VAFC is good for up to 440-450 cc using the 'hack'. If you go the 'hack' route, you'll still need some sort of boost/timing control, so you would need to leave in the JR BTC or get something else, like a J&S. 440 cc is the smallest injector I would run with the JRSC if not using some sort of rise rate FMU. Some have done it, but I really don't recommend mixing methods, it can get messy if something goes wrong. Either run large injectors, or run stock injectors and an FMU.

funnieguy · 02-07-2005, 10:12 PM

I ran 550's on my prelude, but I didn't install the fuel pump, or the fuel pressure regulator. You wouldn't need it. I was also running on an AEM EMS though.

luder621 · 02-11-2005, 08:42 AM

Ok, so I just got my car back from the shop yesterday from major engine work. Turns out my knock sensor was busted among many other problems. ANYWAY, I've got my JR FMU cranked all the way, the shop said I've got around 100psi fuel pressure. I don't know what my static pressure is. I plan on getting it tuned, but still don't think I'm getting enough fuel. I've been taking it easy since I just got the engine done, but under full throttle at lower RPM's (3-5k) my autometer a/f reads anywhere from dead middle stoich to right between stoich/rich. I didn't read enough and had the shop throw in 550cc, but that didn't work. Is something wrong with my injectors? I think I need bigger ones but what size and do I need a new FMU with those? Would I use the bigger fuel pump with bigger injectors? I'm about to give up on this cause it drives like junk. When I let up on the gas from a full acceleration, I get a little hiccup also. I know I have to get it tuned but I want to make sure I can get enough fuel before wasting my time and money on the dyno. Any ideas? Oh yeah, I also have a VAFC but I haven't changed anything.

sharkcohen · 02-11-2005, 09:24 AM

Dude, you are throwing random stuff at your engine. You don't use 550 cc injectors with a boost dependent rise rate FMU. If you are going to use the JR FMU, you need to put the stock injectors back in. Your stock ECU does not know what to do with 550 cc injectors, you cannot run them without programmable management. If you want to use the 550s, you need to use programmable engine management, such as Hondata, AEM EMS, or EFI PMS.

If you use the JR FMU, you MUST use the fuel pump supplied with the kit. If you use large injectors and programmable management, you should use the stock fuel pump.

Stop boosting on the engine!!! You shouldn't be boosting on it if things are not working properly.

luder621 · 02-11-2005, 09:50 AM

I'm sorry for the confusion, the shop put my stock injectors back in after the 550cc didn't work. The situation I explained is with the stock injectors. I know I can't use the 550cc, my question is how do I get more fuel, what injectors, FMU, etc.

Paluce · 02-11-2005, 12:39 PM

Here's your options...

-stock injectors, hi flow pump, JR EMS (FMU)
-550's w/hondata or AEM EMS, no hi flow pump needed, and No FMU!
-440's with the VAFC hack. (need to search for all the instructions)

luder621 · 02-11-2005, 01:04 PM

Alright, well the stand alone is out because I have an SH. Haven't heard of the VAFC hack, I'll have to search for that. Currently I have the stock injectors with high-flow pump and JR FMU and it isn't enough fuel. Has anyone else ever had a problem with this set-up??? If not could clogged injectors be the problem???

sharkcohen · 02-11-2005, 01:18 PM

Do you have a fuel pressure gauge?

luder621 · 02-11-2005, 01:35 PM

I do not have a fuel pressure gauge (thought I realize now how much I need one). The only info I have relating to fuel pressure is that the shop said I was running around 100psi fuel pressure. I'm assuming he found that when he had all his electronics hooked up to the car, therefore that wouldn't be the static pressure. I searched, but what are my pressures supposed to be? Is it at all possible to have a bad FMU??? Or to have the lines switched going in and out of the FMU? I have another FMU so I could switch it out, or is this not at all possible....

lennlen · 02-12-2005, 12:31 AM

idle should be 50 ish, static should be 70-75, WOT should be 100-110+
Turning the bolt on the JR FMU only changes the static pressure, you need a fuel pressure gauge if you dont have one yet. Another really important thing is that you CANNOT TRUST YOUR A/F GAUGE, might as well sell it.

You are bogging because your static FP (on the JR FMU) is set too high (since you say your FMU is cranked all the way up), you need a FP gauge to set it to 75psi STATIC to be safe. (BTW, in case you were wondering, static FP is just as you hit 0 Psi of boost, or just as you're comming out of vacuume)

sharkcohen · 02-12-2005, 10:31 AM

For further clarification, 'static' pressure is at idle with the vacuum line disconnected from the JR FMU.

luder621 · 02-14-2005, 08:23 AM

I've read the underhood fuel pressure gauge install and was wondering if taking a fuel pressure reading at the output of the JR FMU is just as effective? I know the install is right before the fuel rail and I'm assuming that is because it is after the honda FPR?? How will the pressures differ? Thanks.

sharkcohen · 02-14-2005, 04:45 PM

That will not work, it will not tell you the working pressure seen at the injectors.

luder621 · 02-16-2005, 08:24 AM

Alright, well I'm taking the car back to the shop tonight and they are going to check all my wiring and take some fuel pressure readings and see if that does anything. In the meantime, i think I just might not be able to get enough fuel with the JR/stock set-up (I've read this has happened a couple of times). I even swapped out my JR FMU, cause I had 2, and it is still behaving the same way. I think I might just go with bigger injectors and FMU. If I wanna do this route, what size injectors (310cc or 370cc) would be best and which FMU? I've read many people with the Cartech 2025...is that the best for our application? Also is it a matter of just switching the cartech for the JR FMU? Is there any other lines I need to run (i.e. vacuum, etc)? I'm guessing that this FMU would still be used alongside the honda FPR and it doesn't replace it right??? Thanks.

TwizT · 02-17-2005, 05:58 AM

Quote:

Originally Posted by luder621

I think I might just go with bigger injectors and FMU. If I wanna do this route, what size injectors (310cc or 370cc) would be best and which FMU? I've read many people with the Cartech 2025...is that the best for our application? Also is it a matter of just switching the cartech for the JR FMU? Is there any other lines I need to run (i.e. vacuum, etc)? I'm guessing that this FMU would still be used alongside the honda FPR and it doesn't replace it right??? Thanks.

I think it's time for a new shop....sounds like their milking you for everything you got and providing solutions that will require you to come back. With forced induction, the EMS is EXTREMELY IMPORTANT !!! You are experiencing all the problems you have because you don't have proper engine/fuel management. Do yourself a favour and just buy an EMS. Either Hondata or AEM. So what if you lose the ATTTS function of your car....atleast you will have a car that runs properly, and you reduce the chances of blowing up your engine because of improper engine management. If you're going forced induced, do it the right way. You'll end up saving yourself from grief and save money in the long run.

luder621 · 02-17-2005, 06:19 AM

Well actually this shop is trying to figure out what the guy did that I had install the kit. I'm probably gonna go with bigger injectors and a cartech FMU. I've heard some good things about this combination.

luder621 · 02-18-2005, 08:01 AM

Alright, well I just talked to the shop and after checking my wiring, they basically reinstalled the entire JR electrical system. They said it is running 10 times better and it seems to have cleared up my issues. I will take it to the dyno to be sure. LET THIS BE A LESSON TO EVERYONE THAT GOES FI, don't skimp on the install. I had a friend of a friend (a mechanic who races DSM's) do the install and his mistakes cost me an engine. Pay the $1k to have it put in the right way. Also, any problems with the fuel/timing, double/triple check your wiring. I always seem to learn my lesson the hard way, but at least I have a rebuilt engine that should run great for a while now. Hopefully my saga ends here. Thanks for everyone's help and suggestions.