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Discussion Starter · #1 ·
Has any ST2 owners messed around with their injectors to improve performance.
I compared the ST2 injector type to the ST4 from the parts list and noticed it is a different part number.
I'm wondering if there could be an opportunity to get a greater fuel air mixture into the engine by trying the ST4 injector type, not sure if the internal diameter of the injector body on the ST4 is bigger than that fitted to the ST2.
Carburetor engines seem to get performance gains by fitted bigger diameter carbs, so why not the same for injector engines.
 

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Mr Leakered
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I don't believe that I've heard that the injectors are a weak point in the system. Folks will go with bigger injectors when the existing ones can't provide enough full at 100% duty cycle. I haven't heard of lean running at high RPMs.

If you have significantly changed the displacement. Then that might be a different story.

Have a good one.
 

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I believe that you are confusing the throttle body's with the injectors when comparing with larger carburetors. I have a ST4s that I had the heads done up/set squish/degreed the cams as well as the open air box lid/exhaust can combo, when I dyno tuned it was running lean at high revs with the injectors at 100% duty. At that it was producinng 121hp. I increased the fuel pressure and ran it again which showed another 2hp. Can't speak for a ST2 but unless you are running out of fuel there would be nothing to gain.

Jerry
04 ST4s (100,000+km)
 

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He may be talking about spray pattern/# of holes in the injectors and how that might affect fueling/performance.
 

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I suspect my ST2 is running rich. That means unless you have already improved airflow, and possibly other things, you probably will not see any performance gains from larger injectors. I would suggest pipes, air box mods or K & N filters, and either a chip or a power commander.
 

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When I read Tims post again I'm pretty sure that he means the throttle body's. Still not sure if it would help much as most early Ducati's are valve limited, it is hard to make any substantial power gains without addressing that area first.

Jerry
04 ST4s (100,000+km)
 

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When I read Tims post again I'm pretty sure that he means the throttle body's. Still not sure if it would help much as most early Ducati's are valve limited, it is hard to make any substantial power gains without addressing that area first.

Jerry
04 ST4s (100,000+km)
Has any ST2 owners messed around with their injectors to improve performance I compared the ST2 injector type to the ST4 from the parts list and noticed it is a different part number. I'm wondering if there could be an opportunity to get a greater fuel air mixture into the engine by trying the ST4 injector type,not sure if the internal diameter of the injector body on the ST4 is bigger than that fitted to the ST2.

Carburetor engines seem to get performance gains by fitted bigger diameter carbs, so why not the same for injector engines.
He does allude to both injector type and tb/carb throat width. Valve area may limit performance re breathing, but better atomisation of the charge from an injector with a different head or with a whole TB assembly with a different injector angle could increase power or improve running. Look at some of the improvements the MTS12 has made for 2013. One of them is a differently angled injector spray. Did the same with the Khein carb on my HD. Adjusted the angle of the accelerator pump injector and it ran better. :) :)
 

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The 2V and 4V (inc. the ST3) Ducatis use completely different throttle bodies. They will not interchange. 2V are a side by side arrangement and the 4V bikes use a forward to aft arrangement. I think the injectors are also physically different. If you're lean and at max duty cycle on the injectors, what did you do to the engine?

You might pull the injectors and have them cleaned and tested if you feel they are not delivering. Increasing the duty cycle (by adding more fuel with something like a PC3 or a performance chip) will do nothing if the injectors are dirty, as these bikes are open loop and deliver fuel based on the assumption everything is adjusted properly and clean. No regard for how it's actually running. No feed back to the ECU.

The ST4, ST4s have the same 46MM throttle bodies as the 916 and I think 996 (748s have 44MM, even though they look the same). I've read conflicting info on the ST2. Some places say 42MM, others say 45MM. In any case, it doesn't matter as you would not be able to fit the 4V TBs to your 2V bike.
 

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Ducati actually increased the throttle body size (I believe 50 mm) as well as shorted the intake cam duration (10 degrees) on the ST4s. I have no idea of the size of the ST2 throttle bodies but I am sure that they are built differently as mentioned as the intake boots are much longer & offset. On the 4v bikes the intake boots are short & straight.

Jerry
04 ST4s (100,000+km)
 

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Ducati actually increased the throttle body size (I believe 50 mm) as well as shorted the intake cam duration (10 degrees) on the ST4s.
True regarding the cams, but the S4 and S4r (I think ST4 also) have these cams too. Not true on the ST4s 50MM TBs. They are 46MM. They measure 50MM at the top, but taper down to 46 below the butterflies. I have an old set off my 2003 ST4s laying around that I just measured to be sure. The 748 TBs measure 50MM at the top too, but they taper down to 44MM.
 

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True regarding the cams, but the S4 and S4r (I think ST4 also) have these cams too. Not true on the ST4s 50MM TBs. They are 46MM. They measure 50MM at the top, but taper down to 46 below the butterflies. I have an old set off my 2003 ST4s laying around that I just measured to be sure. The 748 TBs measure 50MM at the top too, but they taper down to 44MM.
True enough, I was misled by a magazine article. I looked it up & they actually downsized from the 996. My apoligies

Jerry
04 ST4s (100,000+km)
 

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Larger injectors can make a difference on a TDI, as does a chip. That is what lead me to consider installing an aftermarket chip on my recently acquired ST2. I found a Fast By Ferracci chip on eBay. The difference is subtle, at least it is now. My bike is completely stock. After installing it I started noticing a bit of fuel smell when I start it up. That is why I suspect I'm running rich.

I went back and forth between the stock chip and the FBF chip the other day. A guy riding behind me agreed that he thought I was running a bit rich. The interesting thing is he noticed it when I was running the stock chip. I am going to experiment with removing the air box cover.

I plan to put an aftermarket exhaust system on as well. Hopefully sooner than later. I am a little hesitant to make any changes to the mixture pot until I do a bit more experimenting. I will probably mark the present location and rotate the pot a bit to see how it runs. I am considering investing in a sideband so I can have a better idea of what is going on. For now I am going to remove the plugs and see how they look and smell.

I suppose injectors could make a difference, but I'm inclined to improve the breathing and the fuel map first. Hence my suggestions to the OP.

Does anyone know if there is a power commander made for an ST?
 

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Mr Leakered
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I considered a wideband for a while, but you'd need bigger bungs welded to the headers.

Don't have any fear of the trim pot. I know the ST2 is a bit different, but I leaned mine out until I got lean running then backed it off a little.

Have a good one.
 

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Life is too short to worry !
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The days are getting longer!
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Larger injectors can make a difference on a TDI, as does a chip. That is what lead me to consider installing an aftermarket chip on my recently acquired ST2. I found a Fast By Ferracci chip on eBay. The difference is subtle, at least it is now. My bike is completely stock. After installing it I started noticing a bit of fuel smell when I start it up. That is why I suspect I'm running rich.

I went back and forth between the stock chip and the FBF chip the other day. A guy riding behind me agreed that he thought I was running a bit rich. The interesting thing is he noticed it when I was running the stock chip. I am going to experiment with removing the air box cover.

I plan to put an aftermarket exhaust system on as well. Hopefully sooner than later. I am a little hesitant to make any changes to the mixture pot until I do a bit more experimenting. I will probably mark the present location and rotate the pot a bit to see how it runs. I am considering investing in a sideband so I can have a better idea of what is going on. For now I am going to remove the plugs and see how they look and smell.

I suppose injectors could make a difference, but I'm inclined to improve the breathing and the fuel map first. Hence my suggestions to the OP.

Does anyone know if there is a power commander made for an ST?
Did you try adjusting the trim pot in the ecu after swapping chips? This can make a big difference.
The air box mod will also effect this. I suggest removing the top completely and starting from there. Go large or go home. :yeah:
 

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I have not made any adjustments yet. I think it runs slightly rich with the stock chip, and maybe just a tad richer with the FBF chip. I was going to pull the air box cover and take a test ride yesterday, but was too busy. I plan to do a bit of experimenting and figure out how to get my bike dialed in. I'm hoping fuel economy will improve when I do. It seems to get about twenty-five to the gallon now. That seems low to me since I have ready about people getting forty. I'd be happy with anything over thirty. My bike runs pretty smooth now so I'm not going to rush my changes.

Thank you for the input.

To the OP, not meaning to hijack, just wanting to add value you may find interesting too.
 

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Discussion Starter · #18 ·
what did you do to the engine?
I have an open top airbox with K&N filter, iridium plus and after market exhaust and chipped ECU.
I've read conflicting info on the ST2. Some places say 42MM, others say 45MM. In any case, it doesn't matter as you would not be able to fit the 4V TBs to your 2V bike.
I measure 42mm one side and 44mm on the other side of my injector bodies.
 

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I have an open top airbox with K&N filter, iridium plus and after market exhaust and chipped ECU.
None of that would require a larger injector or throttle body bore. Those are standard "bolt on" mods that have been done for ages with excellent results. If you're thinking it's too lean like that, first try a proper base line set up (TPS, sync, idle / CO set). If you can't get that, troubleshoot the problem and repair. Bad TPS? Dirty TB idle jet passages? Dirty injectors? Faulty ECU or Chip? Faulty air pressure, water temp, air temp sensors?

I guess the natural question should be: Are you having a running issue, or do you feel there should just be more power given the bike and your mods???
 

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Discussion Starter · #20 ·
I guess the natural question should be: Are you having a running issue, or do you feel there should just be more power given the bike and your mods???
No not really, it's a bit thirsty and I had the CO2 checked at the last service which included shims & belts.
It doesn't pull the top speeds on standard gearing, or I'm frightened or mechanically sympathetic to rack the nuts off it. I've seen it pulling 9.5k rpm in top but not at the quoted speeds.
I tried 14/40 gearing from the standard 15/42 and can just manage 130+.
 
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