Twin Injectors

Bridgland

Maybe an odd question, but I thought I would ask anyway.

Is it possible and is there any benefit to put twin injectors setup like the SP4/5 on a 888 Strada engine?

If so what ECU and Eprom changes need to be performed?

Thanks.

danbrisbane

Like to know same, I have 89 S3 strada motor and also interested in easy performance upgrades, that wont destroy the cases etc. cheers

dudlington

In my opinion .......... NO

Someone might correct me but the single injector system on the Strada can flow enought fuel for 120 hp. Not sure it that is RWHP or not (Anyone any ideas ?). Basically you can,t just chuck in more fuel (From a twin injector system) without firstly more air , then you need larger valves or the very least longer duration cams to get that fuel out of the cylinder. Then of course you need to further get the stuff out with a good exhaust system. You would also need to modify your cable harness to fire the extra injectors as firing them all at the same time with double the fuel will not work. You will either need to modify a P7 (To fire the second injectors at certain higher revs) or just use a P8 computer with a good chip. I think that might cover it or ????.

Simple cheapish performance gains can always be had by a better air filter and exhaust with a slightly richer chip. After that it will get more expensive...................

brad black

in the p7/p8 format, the twin injectors are run individually, and when running on two the map value pulse width is cut in half. so you don't get any more fuel as such, but you don't run out of time to run the injectors up to 100%.

so you still need appropriate sized injectors. the black or red ones fitted to the 851 kit/sp/sp2/3/4 are all too small, and the fuel map has ff on it - the biggest pulse width available. not the same thing as duty cycle. the sp5 uses the green side flow injectors, whcih flow the same as the green end flow used as a single in the 851 strada. why they didn't use them in the sp i don't understand.

rpm and power output are the two factors that combine to cause a single injector to run out of fuel. a 748sps will run out of fuel around 12,500rpm from memory if you can keep it making power.

an st4s will make 120hp on a single @ 3 bar. 3.5 bar will give you an extra 8% should you need it. i did a 916 with sps cams that was running out around 9,300 rpm - it wasn't anything special.

with the 1.6m ecu the injector pulse width can be factored down from the map value in increments of 1/32, with all injectors run at the same time. on the 996 they were run at half the map time, on the euro 996s they're run at 9/16 of the map time. the 748r also uses the 9/16 factor, but with a single, much larger injector.

Mr.R

I'll simplify what Brad's posted...

Unless your motor is kicking out over 130 rwbhp there's NO point in fitting twin injectors per cylinder.
The Green's fitted to the Strada single injectors provide enough fuel to make 130 rwbhp.
Adding extra injectors per cylinder won't make any more power, unless the motor is tuned to make more power than the 130 rwbhp that the single Greens can provide.
Just chucking in more fuel won't gain power unless the motor is tuned to burn the extra fuel and air.

My 916cc 851 makes 128 rwbhp @ 9,200 rpm and at NO time does it run out of available injector time, despite running single injectors with the throttle bodies bored out to 54mm.

So to sum up...
Single Green injectors per cylinder are more than up to the job.
Twin injectors per cylinder are a waste of time unless you're super tuning your 851/888 motor.
...and that includes the SP 2, 3, 4, SPS and SP5's

Steve R

dudlington

Single Green injectors per cylinder are more than up to the job.
Twin injectors per cylinder are a waste of time unless you're super tuning your 851/888 motor.
...and that includes the SP 2, 3, 4, SPS and SP5's

Probably the point of putting the twin injectors on the SP bikes was to homologate the injection system for the race bikes !!!!. They would have for sure got a benefit from it.

brad black

i don't think the reasons behind going 4 injector were that forward thinking. and this bike was first a race bike before being a road bike as such. the p7 has the capacity to run 4 injectors individually, so they used that. it has a lot of race bike cool about it.

the corsas always ran 5 bar fuel pressure because the black/red injectors they fitted were too small, even for the road bikes. there's no way they could have run them on a single. i'm not sure why they fitted the injectors they did, or when the green ones became available to them to be fitted to the 89 models. maybe they fitted what they had at the time. they never bothered doing anything more engine development wise for the sp2/3/4 past the tri kit, even if the eproms do all vary slightly.

dudlington

brad black wrotei don't think the reasons behind going 4 injector were that forward thinking. and this bike was first a race bike before being a road bike as such. the p7 has the capacity to run 4 injectors individually, so they used that. it has a lot of race bike cool about it. the corsas always ran 5 bar fuel pressure because the black/red injectors they fitted were too small, even for the road bikes. there's no way they could have run them on a single. i'm not sure why they fitted the injectors they did, or when the green ones became available to them to be fitted to the 89 models. maybe they fitted what they had at the time. they never bothered doing anything more engine development wise for the sp2/3/4 past the tri kit, even if the eproms do all vary slightly.

Brad are you aware on the 748R and 996R that Ducati Homologated a special shower injection system specifically for racing but had to homologate it for the road first (Promise to build min 500 road bikes). They also made special mods to frames for the injection units and to get larger airboxes (Again for HP advantages). The frames for the 748R and the 996R are the same and are unique............it is no coincidence that Ducati won the WSBK on the 748R and the 996R..............just thinking that this mindset was earlier also. Let be honest it was WIN RACES ON SUNDAY AND SELL BIKES IN DEALERS ON MONDAY.

nine16

With the 996cc ST4S based motor build (crank/rods/pistons/cams), I kept the ST single injector throttle bodies to keep the wiring and components as straightforward as possible. Since the green injectors were 15+ years old, I wanted to start with a clean and even slate so I had them serviced--cleaned, matched, and bored to flow 450 instead of 330 cc/min, fresh o-rings, etc. I did use an adjustable fuel pressure regulator to give it a very slight increase to 3.5 bar and then we started more or less from scratch with the mapping. In the end, 3.5 bar shouldn't be stressing the (new) fuel pump and the single injectors aren't getting too close to max duty cycle.

Mr.R

With the 955cc motor that I'm just about to fit to my 851 I'm expecting around 140 rwbhp, I'm still going to fit single injectors per cylinder.
I won't be boring out my Greens though, rather I'll be fitting larger injectors with more holes and a better spray pattern that will flow more fuel.
I've NO DOUBT what so ever that the new single injectors will flow enough fuel to make my target power and torque.

Steve R

dudlington

Mr.R wroteWith the 955cc motor that I'm just about to fit to my 851 I'm expecting around 140 rwbhp, I'm still going to fit single injectors per cylinder. I won't be boring out my Greens though, rather I'll be fitting larger injectors with more holes and a better spray pattern that will flow more fuel. I've NO DOUBT what so ever that the new single injectors will flow enough fuel to make my target power and torque. Steve R

Steve I am sure the above solution will give you what you need and seems a lot simplier than going over to the twin injectors per cylinder. I guess at the time (30+ years ago) there were reasons for Ducati to do what they did , but I guess technology in injection systems/ECU,s has moved on and made the twin injection units kind of redundant. Even the Panigale 1199S only uses single injectors per cylinder. My 1199S with Race Termignoni exhaust and tuning chip/filter gives close to 190 RWHP all on single injectors.................kinda makes you wonder ?????.

brad black

dudlington wroteBrad are you aware on the 748R and 996R that Ducati Homologated a special shower injection system specifically for racing but had to homologate it for the road first (Promise to build min 500 road bikes). They also made special mods to frames for the injection units and to get larger airboxes (Again for HP advantages). The frames for the 748R and the 996R are the same and are unique............it is no coincidence that Ducati won the WSBK on the 748R and the 996R..............just thinking that this mindset was earlier also. Let be honest it was WIN RACES ON SUNDAY AND SELL BIKES IN DEALERS ON MONDAY.

pretty aware, yes. the 748r didn't win too much, it was too heavy and too slow. the showers started with the 97 or 98 model corsa, which had 3 injectors and individual operation, not sure if they ran the p8 or mf3 initially on them.

not really special, just changes for new production models.

brad black

you can run anything on a single injector if it flows enough.

if you're talking oem parts in oem desmoquattro fitments there are limits to the single.

if you want to up-spec them injector flow or fuel pressure wise then of course they will support more power. it's not rocket science. work out how to mount a pico style iwp189 from an 1198 in the 851 throttle bodies and you'll be fine at 3 bar.

it's not as simple as power level though, it's a combination of power and rpm that causes issues for oem fitment single injector systems. for example, when we advance the inlet cams in a 996 they make more power, but have less injector time issues as the torque peaks lower and fuel requirement is more about torque (well, volumetric efficiency) than power. although the efficiency drops the higher you go above the peak torque rpm, so the fuel requirement doesn't drop as fast.

Mr.R

Well after todays efforts (and some investigation over the last few days) I've bought some Pico injectors capable of flowing enough fuel to make 170 rwbhp.*
With very little work making up some parts to mount them they practically drop into the top feed 851 TB's.
These Pico's are 4 hole pattern that give a very good cone spray paten, making good power.
No modification is needed to the OEM TB'S!!!!
In fact they pushed into the 851 TB's and the work involved was to make sure that they didn't fall out or get blown out by a spit back into the airbox/TB's.
They cost me £180 for the pair, the wiring/electrical plugs fit straight on as do the fuel connections on the standard 851 hoses.
I can run them at 3bar taking a lot of stress away from the small '92 onwards fuel pump...
RESULT! 😎

*There are other Pico's available that will flow a LOT more fuel that will still almost drop into the 851 single injector TB's and they don't cost anymore.

Steve R

dudlington

[QUOTE=Mr.R;72103]Well after todays efforts (and some investigation over the last few days) I've bought some Pico injectors capable of flowing enough fuel to make 170 rwbhp.*

Of course flowing more fuel is only 1/14.7 th of the equation (stoichiometric air-fuel ratio)...........1 more bit of fuel in means another 14.7 times air needed as well . I think the air will be the bottle neck unless you make mods to the standard set up. Since the early 90,s manufacturers have been producing motorcycles with ram air/pressurized airboxes for good reasons. Photo is from my sealed airbox using racing conveyors , single injectors , 1198 engine in an 851. Nearly 170 Hp @rr wheel.

Steve any chance of some photos or part numbers of those injectors............sounds interesting.

brad black

what colour pico did you get?

Mr.R

brad black wrotewhat colour pico did you get?

Hi Brad,

They're White's.
I could have gone for some that flow less (somewhere close to the OEM Weber "Greens"), but the next size down would only flow enough to make 140 rwbhp and...
As I'm hoping to hit around 140rwbhp from my 955cc motor, I wanted a bit of leeway.

Steve R

Mr.R

[QUOTE=dudlington;72104]

Mr.R wroteWell after todays efforts (and some investigation over the last few days) I've bought some Pico injectors capable of flowing enough fuel to make 170 rwbhp.* Of course flowing more fuel is only 1/14.7 th of the equation (stoichiometric air-fuel ratio)...........1 more bit of fuel in means another 14.7 times air needed as well . I think the air will be the bottle neck unless you make mods to the standard set up. Since the early 90,s manufacturers have been producing motorcycles with ram air/pressurized airboxes for good reasons. Photo is from my sealed airbox using racing conveyors , single injectors , 1198 engine in an 851. Nearly 170 Hp @rr wheel. Steve any chance of some photos or part numbers of those injectors............sounds interesting.

Of course Paul I don't expect to hit anywhere near 170 rwbhp with my 955cc motor, but the next size down would "only" provide enough fuel to make around 140 rwbhp and I wanted a bit of leeway with the fuelling.
I'm fairly sure that my 955 motor fitted with T1 cams timed to my preference, 37/32mm valves fitted into modified "G" heads, 54mm TB's, 3 piece carbon Corse airbox, carbon runners and a full 50mm spaghetti system will flow enough air to need injectors that will flow enough to make at least 140 rwhp.
Which will be not too bad for a "Desmoquatro" motor with 851/888 top end stud spacing.
Another bonus (one which I didn't expect) is that the new Pico injectors have saved another 1/2 lb off the all up weight of the bike.
I've had the electronic scales out and the weight saving surprised me!
I'm getting very close now to 360lbs fully wet with every little mod chap.😎
If you recall my personal target was to build a 851 with a fully wet weight of around 360 lbs, with a RWBHP figure of around 140 at under 9,500rpm.
My youngest son is in the USA at the moment, but when he gets back he's promised to help me load up some pic's of this project.

Steve R

dudlington

Steve R
Your last quote I think has a mistake in there : " If you recall my personal target was to build a 851 with a fully wet weight of around 160 lbs ".............BLIMEY a way to go then !!!!!...............Just joking. 360 lbs is a low low weight and 140 rwhp will make it fly depending on your weight of course.

Mr.R

LOL...Now corrected.😱

Just boxed up the bottom end finally, I'd found a problem when fitting the modified 916SP crank into later S4R/ST4 cases.

The flanks of the crank were hitting the main bearing bushes, making it very hard to set the end float using my dial gauge, so after heating the cases and removing the bushes to machine the inner faces down, 1mm off one and 0.75mm from the other, that sorted out that little problem.

It was then that I spotted another small problem...
The later "Red bolt" cases have a drilling to squirt oil up under the piston crown, however the drilling didn't line up with the groove in the main bearing bush, so the squirt hole on the LH side cases wasn't going to work anyway???
These are "NOS" cases FFS! Well down Ducati.😏

So it was out with the trusty drill and Dremel to make a small groove to allow the oil to actually get to where it was supposed to go in the 1st place.
Lucky the 1st problem showed up or I wouldn't have found the 2nd one.

Anyway it's all done now and the bottom end is all boxed up, now it's on with the rest of the motor.
It's not like all of this is actually holding me up though, my now checked and modified frame is away at the powder coaters along with my chrome moly Corse clip on's, white for the frame and satin black for the bars.

Steve R