I finally had some time to install the 370cc injectors. It took me two nights to get it done but it appears to be a success. I did this with out a reprogrammed ECU, so I had a few challenges. My plan was to use an adjustable fuel pressure regulator to lower the base fuel pressure and see if the ECU could learn the larger injectors from O2 feed back, it appears to have worked.

I set the adjustable fuel pressure regulator to the lowest it would go ~20psi, and fired it up. It idled like crap but it stayed running. There was a visible plume of smoke coming out of my exhaust and the fumes were very strong. The EGTs weren’t even registering so they were below 300c and my AFR light wasn’t cycling. I tried to use my Fields AFC to lean it out but it just idled worse so I set it a zero. I backed it out and went for a spin, it had no power and bucked a little too. I took it on to a main street and got it up to speed, the power was getting better but still wasn’t great, EGT’s never got above 400c. I tried to lean it out again with the Fields AFC but it ran worse and even backfired, so I set it back to zero again. I then tried to nail the throttle and see how it reacted with some boost. It wouldn’t even go, it just sputtered and barely accelerated, I still had the 8:1 FMU disc in so the fuel pressure was way up. I drove it around for a little while and went back home. I swapped in a 6:1 FMU disc and put it up for the night.

This morning I got into it and it and it started up fine, a little rough but ok. The EGT’s came up a bit more also. I then switched on the AC and it idled very well. I backed out and headed to work. It was a little rough at first but began to feel considerably better and the EGT’s were looking closer to normal. I got on to the highway and nailed it, and to my pleasant surprise it took off pretty darn strong, the EGT’s went up to ~700c peak in third gear at redline. So for the rest of my 20-minute drive to work cruised in fifth at 60mph and the AFR gauge started to cycle and the EGT’s got into the normal range also. When I got back on to the surface streets the car was idling fine and part throttle acceleration was good, the EGT’s were almost perfect also. I took it out for a spin at lunch time and it ran just fine, part throttle and idle EGT’s are on the money but WOT EGT’s are still low at ~700c. I’m going to put the 4:1 FMU disc in tonight and give it a spin to see if I can get the WOT EGT’s back up to the 760c-800c range.

My next steps are to do some EGT comparisons. Before I swapped the injectors I did a long test run in which I recorded the EGT’s in ever gear in 500 rpm increments from 1500 to 6000. I will repeat the test run and record the EGT’s with the 370cc injectors to see how close it really is. After I get that done and am satisfied with the open loop operation of the car I will slap on the 2.62” pulley and head to the dyno to get the WOT AFR tuned.

So it appears that it is possible to upgrade the injectors on a 4th gen with out the expense of a modified ECU. I went this route for a few reasons. With a modified ECU and 370cc injectors the limit of power is ~410bhp or ~338whp, I plan on going past that by a fair margin. I also have dyno’ed near that level already so my next choice would have been Nismo 550cc injectors for ~$900 a set gray market, no thanks. I decided to keep the boost referenced FMU and tune it my self. I also have not seen any remarkable power numbers come from a supercharged Maxima using a modified ECU. I’ve had several conversations with the ECU tuners and they all were for the most part very vague and uninformative. What I guess it really comes down to for me is because I can not put my car on their dyno do I want their best guess for my ECU programming? Their best guess is usually very conservative for safety sake. So I’m just going to continue to DIY and spend some time on my local dyno and tune it more aggressively then an ECU tuner would guesstimate.

 

Sounds like it's going well.

If the 4:1 is even better, you can get the 3:1... that way you can raise the base fuel pressure back up a bit... This will help your throttle response... I'm sure it's not great for fuel atomization with a 20psi setting...

 

Yea, 20psi isnt good for atomization. I'm sure my fuel milage will suffer a tad for it. It goes up to ~25psi when the vacume goes away under acceleration. I'm actually amazed that I didnt have to use the AFC to do any corrections yet, all fuel preussuer and the ECU is hanging in their and learning.

 

wow, awesome work! How I dream of having money for boosting and playiing with mods like this....

Well anyway, it's really awesome to read about it!

 

I bet you can hit the 400hp mark.

 

I got to say, your one of the few that actually try new things on the max. I give you many many props on this..

 

I think what you confirmed is that the ECU really does learn new parameters. It took awhile for the changes to be permanently saved in the ECU, but they eventually changed.

I bet that you can step-by-step dial-up the fuel pressure incrementally...maybe 5 or 10 psi per day...until the idle pressure is back to stock levels. However, you may run into a condition where the MIL light will go off and throw a code for excessive adjustment required. At that point, the ECU will no longer be able to compensate.

The only minor downside to running the stock ECU in your case is that all the learning is removed when the battery is disconnected or the ECU is reset...at which time you'll have to go through all this again. Still, pretty minor downside considering you don't have to shell out $$$ for a custom ECU.

 

Wow

*drool*

 

I'm shooting for 350hp at the wheels SAE with no nitrous and 425hp at the wheels SAE with some juice.

 

Nice going!

 

kevina's next mod?

 

good lord, do you ever stop modding!! SWEET...and thanks for answering my nitrous question the other day!!!!

 

Another Maxima milestone!!!

Great work!!!

 

Good lord Matt! It's never enough for you is it?


I'll be happy if I can make 300hp at the crank.

 

DAMN props for trying something new, keep us posted.

 

Good job Matt, your truly a pioneer...


BTW, how do you think this would work on a NA Max, say running a 125-150 shot of nitrous, will they handle over 95psi of fuel pressure?

 

Cool beans dude. Thats almost exactly what I ahd been thinking about doing later down the road. Except I have been looking for the LS1 style injectors (thats whats needed on the VQ35).

If you're shooting for the 400 mark then don't take too long doing so because Im right behind you .

As for the ECU, it's only going to be able to adjust but so much. The block learns probably don't have enough range to get your 370cc injectors back upto normal operating pressures. A trick you probably should try is to recalibrate your MAF like the Mustang guys do. If there isn't a good way to do that you could get a Vortech or C&L 73mm Mustang MAF and plug the ford or a Nissan probe into it (thats exactly what I used to do on my SE-R). That way you could simply change out the sample tubes in order to better tune the mixture.

 

good work matt..

 

I think they will work fine on a NA Max as long as you have an adjustable FPR. Adding the juice will be trickey because the injectors will flow so much more fuel as pressure increases. I would guestimate that with this set up you would go from 25psi base FP to ~35 to ~45 for a 100hp shot. If you are going to try this start small wit like a little 50hp shot and work your way up. By doing this in small calculated steps you can get a feel for the effect of the dry kits fuel pressure increase and how it effects the fuel flow through the larger injectors. Fuel for 125-150hp will be no problem with 370cc injectors. You may want to consider getting a J&S SafeGuard to get a few degrees of timing retard and some knock protection, and your in luck because their just happens to be a group deal on the J&S going on right now

----------------

I did try the 4:1 FMU disc this morning and the EGT's only went ~20c more to ~720c peak. I was showing ~60-65psi of fuel pressure at peak boost of 9.5psi. 720c is pretty safe for now so I will leave the 4:1 in until I get the 2.62" pulley installed and see how they EGT's look with the extra few pounds of boost.

SR20DEN I PM'd you about the MAF's, thanks!

 

The car is still running just fine. I took it up to ~120mph today on the drive in and then held it at 100mph for a while, EGTs were great and it ran smooth like butter! I got the belt for the 2.62" pulley so with any luck it will be installed this weekend

 

good lord mr. gadget..


2.62??? ddammm.. what psi will that bring you up to?

 

did you have to shave you plate?


if u go smaller than 3.125 u need to shave or the belt will rub??


correct?


or did you figure out a way around that?

 

I may have to shave her down But I've got just the tool for it

 

My god Matt, you are just a monster!

 

Mardigras gets my OMVM award! (One of the Most Valuable Member)

He belongs to the small and elite group of maxima pioneers, who got big ***** and is never adfraid to try new things. We all benefit from them.

 

WOW Thanks for the props!

 

you deserve it dude
its nice to be able to search your posts when i have a question and find helpful answers only a few members have that kinda experience and knowledge

 

So MardiGrasMax, where and how much did you get the injectors for? I am very interested in this little project, but of course, you get all the credit.

Also, OT, but can you PM with the steps needed to convert a Dry N20 kit to a wet and direct port kit? Thanks Matt.......

 

WOW!! .....12's and more wheelspin are on the way As others have said here, you are a great asset to the Maxima community. You definetly have some brass ***** for always running your Max to new levels. Personally, I couldnt do it b/c I would be too worried about making my engine go BOOM. Keep up the good work man!!!

 

I got the injectors from Kyle at SGP Racing in TX. They said they were 96 models with ~30k, he asked for $400 because they were his last set. I offered $350 shipped and he said ok. Others have called and gotten the same schpeal from them about being their last set so its obviouslly not true. Do be warned that the injecotrs dont ship well. The plastic pintle caps are easily broken, they are not available from the dealer. Ask before you buy if the pintle caps are intact or a picture and request that the be wraped individually for shipment. When I got my set from SGP they were all lose on a zip lock bag and the pintle caps were all damaged. Luckily I had a spare set of maxima injectors and was able to use the pintle caps from those on the 370cc's

Perhaps you should talk to 1MAX2NV or SX7R about the proforgger set up, becasue I have done one on a Maxima and they have.

 

not

 

You can get plastic pintle caps from RC engineering!

 

Thanks Ron, But I called them and they said the didnt have them and couldnt get them.

 

Hehe! Like I said before, "always pushing the edge!"

So do you think 480CC and 550CC injectors would be a problem? Turbo95max said he's already pushing the edge for his 370CC, but then again he doesn't have an FMU.

You're always pushing the limits ... that's awesome. No one can keep up! . I was looking at getting 480 or 550 but don't think I should jump straight there yet.

Good job!

 

I think 480cc and 550cc wouldnt work with out a modified ECU. With the 370's and an FMU you could run ~550bhp pushing ~85psi of fuel pressure. I think thats plenty

 

Make sure you get injectors from a 95 or 96 model. The Z injectors changed in 94 and they moved to a different size. I'll search Twinturbo.net and find the info tomorrow for those who are interested..

 

Somethings fishy,
I sent my ijectors to them for balancing and cleaning and they returned them with the oem pintles broken, I called and *****ed and they call tagged them and sent them back 2 days later with new pintles! 96 tt injectors

 

Interesting, thanks again!

 

Only 550??? Hehe... I posted about wanting 600 ... but let's be realistic 400-500 would be nice on a daily driver . What's next on the list Matt ... MAF? You keep bumping the stops!

 

Love your car. You put a lot of time, and the right stuff into it. I would love to see a time slip in the 12's, or better yet a video Keep up the good work, your homepage is very helpfull.