jcorenman

The amount of fuel injected per cycle, for a given power being generated, does not change with larger larger injectors. You need larger injectors at the top end because you are making more power at the top end. More power needs more fuel, but cruising down the highway or even pushing it through the twisties doesn't need more power.

I believe the dampers are sized for the amount of fuel needed at idle and cruise, where injector pulse-widths are in the 1.5-2ms range (net of latency, 2.5-3ms total pulse width). So in theory larger injectors don't matter-- 40# injectors are .75-1 ms instead of 1.5-2, but the fuel quantity doesn't change. So stock dampers should be fine, IF they are left in place.

For an '81 this might be the case, but I don't think it is a valid comparison for LH/EZK based cars.

Batch-fire has no problem idling. This was underscored by an interesting experiment we did recently, as part of a project to look at injector latency. Normally the LH fires once per revolution. If that's an issue, then changing that to once per two revolutions would make it worse, correct? No change. I'll repeat that: No change in how the car idled. If idle is compromised by batch firing, then batch firing at half the rate would have to be worse. (Changing to once per three revolutions did start to make the idle lumpier).

One driver, fires all eight together and normally once per revolution.

AO

Ah hem... except in 89+ plus cars when the Ignition Monitoring Relay is tripped and only 4 fire...

jeff spahn

Andrew, i am sure you meant to say "limp home mode" as so many refer to this

jeff spahn

I am all in for something like this. I'd love to ditch the LH and EZK and move to coil packs. Seems like it would be a fun project.

jeff spahn

Hacker
My car with the Victor kit is now running great. Lots of power, idles very nicely and tuning is right on. I am still interested in this injection idea I am a newbie to tuning compared to you guys but anything that can give us more mileage and more power with more tuning options and we can move to modern electronics running the engine would be cool.
Seems like we could then integrate this into a touchpanel controller for HVAC, audio, nav . . . oh wait that was discussed before and that project withered and died.

victor25

let me follow up on a few things...
The front initial damper is still used in the system, it is just moved to the back.
I have seen this resonance on a few of different plots from other cars not with my kit. The one that first comes to mind was from Tonys twin screw car.
We have no issue with the 36# injectors and dead ended fuel rail that come in the kits. The cars run great. But when people are using large injectors like 60#, there is an obvious resonance. I was looking for a solution to that resonance on the large injectors for when people want to go big with lots of boost. I was thinking after looking at the schematics that this might be a solution. I still think it can be done, but apparently not so easily. The more obvious choice for people that want to go big, is to change over to an aftermarket engine management setup that will allow not only sequential, but also COP and MAP, so that the MAF can be pitched. If there is such a system that is in the works with prefab cabling and programming, then that would make life easy and I will be watching for it.
I have been looking at reworking the drivers side fuel rail and returning to a flow through design with a front damper relocation. I definitely want to continue using the stock fuel rails, and it needs to be a simple solution. There is just not a lot of room available.

jcorenman

Now you are just trying to confuse things

The IMR was added to protect against fires caused by failure of one ignition bank, by cutting 12v power to one injector bank. The LH is still trying to fire all eight on the ground side. Ignition issues are generally wires or coils, the EZK and drivers are pretty bullet-proof.

victor25

Hacker ... I know you are a Murf fan and I have no issue with that. As I have no issue with the Murf system and have recommended it to few people that have the OB cars. The purpose of a forum is to make forward progress and share knowledge. As a moderator I would think bashing would be frowned against, especially when the host company is trying to sign me up for advertising and the like.

FredR

Victor,

I cannot speak for every ST2 user but I can see clearly on my sharkplotter that there are resonance zones with the stock system. As Jim says, the amount of fuel has not changed with bigger injectors but the pulse width drops. The resonance does not occur at top rpm's but something around 2k or so I seem to remember. I do not know if it is a first order harmonic or just the first event we see. 19lb injectors are exhausted at around 400 crank bhp so bigger injectors are clearly justified but 60lb ones? 32lb injectors can crank out around 600 bhp so logic suggests they should be more than adequate.

The problem with bigger injectors is that they are quite possibly going to be timed to such small intervals that at lower rpms and low load values the flow is going to be more choppy and less accurate/reliable metering as a consequence.

As you are modifying the 5/8 fuel rail -presumably shortening it and thus dead heading injector No5 completely, is it not possible to simply modify it such that you have a through flow design retained via side entry or whatever spacial geometry permits? Porsche did not put dampers there because they liked the look of them so they obviously knew something was going on. At low fuel flow rates perhaps the fuel is heating up locally in the rail and leading to other issues?

I cannot say I am surprised that this phenomena is seemingly being amplified. That you have come up with the kit you have tells me you are smart enough to solve this one.

There is nothing wrong with attempting sequential injection- however tuning the batch fired system is enough of a headache for me.

Regards

Fred

Tony

Wouldn't know what it is or what it feels like in my car. Ive got 42#s and boost...runs great. Mixture and drivability are fine. Im all for advancing the technology on the car but if you can get 500hp out of the stock system with the aid of a sharktuner what else more do you need?

What power gains will coil on plug get you? sequential injection? all of it combined?. Personally, I find the gains trivial to the amount of money and time spent to set it up. Now that I have upped my power with boost first, I wouldn't mind adding the finer elements of this type of tuning though..

each his own

victor25

Fred, you are right on track with the situation. We only send 36lb injectors in the kits, but people want to go beyond that or do experimental stuff like run e85 with 60lb injectors. This of course creates things I've not tested or developed for. People will always try to push the limits, and I just want to give them the best product I can to do that with.

FLYVMO

Been reading this topic with great interest, and thought I would share my experience with sequential injection and direct fire coils, that I had installed and tuned on my '86.5 a few years ago. Before installation of the Tec3r my car dynotested at around 250 at the wheels, compression was between 169 and 171 on the cylinder (most at 170). After installing the Tec3r AND tuned on the dyno, the car produced 279 rwhp on the same dyno with zero knock events. Fuel economy was improved noticeably, went from 20-22 to roughly 24-25 mpg highway consistently over a few years. The engine felt livelier and seemed to love the upper RPM range more than before.

Could the stock system have been tuned to the same level? Possibly. There was no Shartuner available back then, and it was my personal preference to have a modern 32-bit computer and new wiring instead of a 25-year old system that was getting more and more touchy and fragile as the years went by. The manufacturer claimed a 7% increase in fuel economy over stock....I got fairly close to that, with an increase in power at the same time. BUT, it took a lot of tuning, both dyno and road driving with a helper in the right seat making adjustments while I was driving.

Would I do it again? Definitely. Again, this is my personal experience, and I thought I would share it.
If one looks at the modern aftermarket options, there are now MSD, FAST and Holley computers with self-learn/self-tune capability far superior to the self-tuning I had available back then.

Cheers!
Carl

danglerb

Main advantage I see with sequential is that its possible to calibrate the flow on each injector by one at a time adjusting pulse width up and down rich/lean and watching the O2 sensor. At higher power levels sequential isn't any different from bank fired, both will be open most of the cycle.

Hilton

Definitely - 85/86 stock tune is now well known to be woeful. A search for porken's threads and chips will shed more light.

Lizard928

I got 320rwhp, and 330rw ft lbs on an 86.5 motor after more tuning. (stock manifolds, H pipe, 2.25")
Prior to the final tune I put down 310/320 rwhp on Louie Ott's Dyno in 2007.....
I tuned aggressively for fuel economy, and saw 30+MPG on the freeway while maintaining the same power.

The high power ignition systems do gain fuel efficiency, as well as power. However the amount of time one can spend tuning the car is unreal. The same can be said for the sharktuner though......
This is why I do a nice curve in the map tailing up and down, doing runs to confirm my AFR, the runs are at different MAP values, and I trim the entire curve up/down. This gives a very consistent AFR, and I tune the ignition relatively conservatively on most engines. The benefit to this is that if something happens and the car goes to a different part of the map, the car will respond identically.
Case in point a local 82 I boosted, he said as he would get into the boost the car would just shut off then come down and reengage. I checked and sure enough the line to the wastegate had broken.
The boost safety shut off (MSII V3.57) was set at 19 PSI. Though I had only technically tuned to 17, the car showed no problems after him driving it like this for two weeks before I found out about it......