HiProfile

I tried asking this over at HMT, but apparently my post was too long to be read thouroghly, and those who clicked the topic had sand in their vagina. That or they started drinking already.

Here's the idea: use small injectors (stock 240cc) with an FMU *and* an ems to deliver more fuel as a trio than the small injectors+fmu or small injectors+ems could in pairs. Again, to avoid confustion, thats using an FMU and EMS <u>together</u> to increase MAXIMUM gasoline delivery with 'undersized' injectors. The theory is that the added *fairly predictable* fuel pressure and added (and subtracted as needed) duty cycle of a datalogging EMS will allow for small injectors to do more work.

I've noticed that almost every sub-650whp honda here follows the trend of "MAX WHP = 0.7 * INJECTOR CC", at least when the duty cycle is given. That's very close to the theoretical maximum power output per injector based on CC size. The only good FMU example I have is my bro's last boosted car, running 303whp with an FMU and 310cc injectors. I can't recall much details, so I can't really use it well.

I really hope this will be an open-minded discusion, rather than an beer-fuel flame fest with a bottomless keg.


Cliff notes: read & comprehend paragraph #2 before you flame.

boostedcivicsir

pm 99lspwr. frank is the only certified btm/inline pump/fmu tuner i know.

with injectors being a little more cost effective at the sub 600whp level, to me it is pointless piggybacking an ems. BUT thats me and i am in no way a tuner. i had a hand in my car but i am not god.

thinking about it more, it would also depend on the rise rate. 12:1 would be more picky than a 6:1.

HiProfile

Well the deal is I'm trying to set up a very low cost turbo kit that I can make multiple copies of, and keep the tune almost the same with crome. I'm shying away from DSM 450's because my friend can get me OBX FMU's at wholesale prices. If its works, but not great, I can always sell it for what I bought it for, and just clean dsm's in my employer's sonic cleaner. I'm hoping for a sub-$500 tag for a complete bolt-on kit (with as little as a minute of o2 tuning) for all the daily drivers around here.

Just so everyone is aware, I try in all cases to use name-brand injectors sized appropriately. My two cars are both street tuned on 93 octane with crome, one with 780cc injectors (for E85 soon).

093turbo16

iTrader: (2)

I think its a bad idea to produce a kit that is going to be "pre-tuned" with an FMU and Crome. Please tell me how you are going to control the duty cycle of the injectors when they are maxed out already? Maybe dial them from 150% flow to 110% flow? IMO its a bad idea all the way around. Don't get me wrong, it will work.. but I don't like it.

HiProfile

I know, I'm just tossing ideas around. I'll be doing the DSM's anyways, its just that the FMU idea got me thinking. Its hard to think of unconventional, yet feasable, improvements for Hondas - virtually everything has been tried.

The thing that got me thinking first was the Synapse FPR, which is adjustable from a normal 1:1 to 2+:1 rising rate. With that you can run very large injectors while idling better. 30-40psi in vacuum, 50-70psi in boost.


As for adjusting the maps, you have to <U>think of it in terms of X rpm at Y manifold psi, resulting in [Y psi * FMU rate =] Z fuel pressure</U>. The rising fuel pressure is semi-predictable - its just the enrichment 'curve' with FMU's that suck afaik (not an FMU guru). The only semi-reliable fmu dyno I know of is my bro's old teg, which he bought with a Drag kit, FMU, an 310cc's. It did 303whp at ~10psi, and I think was leaning out a bit. If that's 100% duty cycle, its ~40% more than the injectors can do w/o the fmu. If you can get say 30psi of fuel pressure at idle and 75psi of fuel pressure at full boost repeapedly, then you can tune duty cycle.

And FYI, the kit I'm thinking of making is $500 max in parts, including the DSM's. $250 injectors aren't economical for this kit on a $150 motor. Although it consists of some shortcuts (clean used turbos, reuse OEM cast manifold, etc), I'm hoping for a *reliable* 99% bolt on deal, with just a few minutes of fine tuning w/datalogging, assuming the basemap is from the same block. Basicly a kit that won't break like an SS auto kit, costs just as much, but includes everything from tuning to oil lines to a 2.5bar MAP sensor. It just comes down to the fact I'm almost broke, about to be laid off one job, have school to pay for, and need to put my skills to work. My Home Depot 'gig' only uses ~2% of my talents on a busy day.

JDMs1eeper

I’ve talked A LOT about this is the past. (Injector sizing and atomization of fuel, ect.) Check out the earlier pages of the LS turbo thread.

BTW for a while I ran Chrome, OEM injectors and FMU 12:1 on a setup of mine w/ good results lol

a few things i tested were:
I’ve ran 106PSI rail pressure w/ 440cc’s to support 367whp
(pump hated me and my injectors were 100% duty from 8300-8500)

I’ve tested gas mileage at 106psi @ 440s VS 60psi @ 1000’s w/ same AFR tune.

Fun stuff.

One thing to worry about is VOLUME; a pump will cry and poo itself while tryin to maintain 1000psi of pressure while supporting volume to support 10000000 HP. The pump will fade on ya.

High pressure can cause your injectors to lock up on you in high RPM/ high duty %’s also

Bunch’a trade offs

093turbo16

iTrader: (2)

I understand what you mean by tuning the duty cycle by changing the fuel pressure, but that does not account for the actual fuel curve. You can't fully tune a fuel map with an FMU. You get one rate last time I checked and can't change the pressure through out the RPM range. Not saying that it won't work, but def take to heart the need for a fuel pump.

JDMs1eeper

ditto! listen to ^ 93turbo16 , john

PrecisionH23a

For the cost of an fmu you could probably find a set of dsm 450cc injectors for the same price.