SleeperGSR-T

Hello HT new member long time lurker.

My jdm b18c has stock internals with simple bolt ons (im, tb, 2.5in exhaust, tial wg @7psi, hks ssqv) still on stock injectors, crome street tune

I very recently rebuilt my used no name .50 a/r t3/t4 & it runs mint.
Overall it's pretty quick (pulls on stock ls1's, 5.0's, 350z's etc)

Besides idle (14.9-15.5) my a/f's are generally on what I understand to be the rich side:
DD 13-13.6
Partial boost with low load 12-12.5
Partial boost high rpms 11.5-11.9
WOT 10.9-11.4

From what ive gathered it should be ok to run as lean as stoich when not boosting and up to ~11.8 at WOT. Im not sure exactly what a good partial boost a/f looks like (the car sees a lot of this during mountain twisties)

I do plan on a retune @10psi or so with rc550's but I have an urge to tinker with an mbc and my afpr.

If I could manage to keep my a/f ratios in safe levels would a little "tuning" via mbc and afpr be too dangerous? I understand my stock fuel injectors will be pushed quite hard running higher fuel pressure. Is there a certain limit where the pressure should absolutely not exceed?

Thanks for opening my first post!

cleansi

do you not have a dyno near by?

jdm_h22

While upping your fuel pressure may result in a little more power, you'll likely be pushing the injectors past a safe duty cycle. (Duty cycle is the amount of time that the fuel injectors are switched on)

It is not recommended to exceed 85% duty cycle. Otherwise you will run the risk of the injector not being able to open and close quickly enough, which causes the injector to float half open. This will lean the mixture out, which is not going to be healthy for an engine at high revs and under full load.

SleeperGSR-T

trashed the crush bent 2.5in exhaust. Got 3in mandrel bent from dp to flow thru mufler, the difference for such A simple mod is huge. Just need to find someone to make me a 3in dp and ill have a complete exhaust setup.

spool time is noticeably quicker and 4th pulls much much harder. the power I was looking for by messing with afpr/mbc is there now so I can wait and save for rc550's and a new tune.

I was thinkin of adding a ball n spring type mbc still in order to keep my wg closed better until we're actually at 7psi. This should help spool time.

Tryin not to pay for dyno time until I tune

SiRCiviC94

how many untuned threads do we have and every single person is RIPPING untuned lmao.

k. so for my curiousity how did you dial this in? do you use chrome yourself?

jdm_h22

Anything less than professional tune and you are asking for trouble. You are essentially "guessing" what your motor needs.. as far as fuel, ignition, etc.. Your tune is absolutely the most important factor in a build.

I guess if reliability, efficiency, and peace-of-mind are not a priority, you could do without.

Yes that's sarcasm

SleeperGSR-T

The car was street tuned by a dude I no longer have contact with.

I figured if all my afr's were proportionally rich then it couldnt hurt to lean the mixture at the afpr.

In any case, I changed my exhaust and it leaned out slightly. About 13.8 cruisin and 11.5 wot. Im not messing with anything now just maybe gather parts to throw on the minute before my next dyno tune

kyden

you can still go leaner at low loads.

SleeperGSR-T

I agree but I dont have tuning software or a laptop for that matter. This means I can only make everything leaner. Thanks for the input tho.

kyden

leave it alone then.