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Discussion Starter · #1 ·
As we all know, Fuel delivery plays a very important roll in the quest of horsepower. What I've done with my 996 race bike was installing 748R throttle bodies. (After I machined the restrictor out) The idea was: bigger throttle body bore = more air going in to the motor, Shower injectors setup = better fuel/air atomization.

I've heard this was a difficult setup to tune before I started the project, and I have to admit its true, now before I switch over to a powercomander and get a custom map for my setup, I wanted to get some inputs from some of you smart guys.



So would a shower injected throttle body be a better setup, or would the traditional throttle body be a better set up?
 

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My understanding is that bigger throttle bodies wont give any increase in HP or flow unless you port and polish then manifolds and heads to go with the larger TB's.

but then again I dont know shit
 

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i don't see why it's hard to tune. it's just a style of fuel delivery. i've played with lots of 748r and have a few combo specific eproms for them now. and all the 749/999 run basically the same throttles. someone who couldn't tune one making the claim to allay the blame?

really comes down to how much time you have to get the air in. early on ducati used long duration cams and not so big valves so there was no point having big throttles leading into small ports. the 748r and now the testastretta engines run bigger ports and throttles and comparitavely short cam durations so they need to move a lot of air quickly. plus they run the biggest injector of that style you can get.
 

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Discussion Starter · #5 ·
To answer brettmess24. The heads are ported and polished and the intake manifolds are bored out as well, and the bike has Hi-comp pistons, flywheel, Ign Amp, cams, 54mm system, ect ect...



Ian. I have seemed to have missed placed my camera... again. Or I would have posted my Dyno sheet. My bike ran 127.6hp and 73.3torque, after the dyno run I changed the fuel regulator, and pressure, bored the throttle bodies, and intake manifolds. I figure that’s good for a little more hp. personally I think if I change the cams, (I'm currently running G-cams) and run a custom map I can get 130hp or more. But what do I no, I'm just a beginner at tuning Duc's.



My question is it possible to produce more HP with the slandered TB's (highly modified of course) or am I on the right track with the shower TB's. I thought this subject could turn out to be a good discussion and I could learn a thing or two.

P.S. Hey Ian. The yellow Duc is faster than the red Duc.:D
 

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mike996 said:
As we all know, Fuel delivery plays a very important roll in the quest of horsepower. What I've done with my 996 race bike was installing 748R throttle bodies. (After I machined the restrictor out) The idea was: bigger throttle body bore = more air going in to the motor, Shower injectors setup = better fuel/air atomization.

I've heard this was a difficult setup to tune before I started the project, and I have to admit its true, now before I switch over to a powercomander and get a custom map for my setup, I wanted to get some inputs from some of you smart guys.



So would a shower injected throttle body be a better setup, or would the traditional throttle body be a better set up?

To put it more simply, an engine is a air pump. Fuel delivery plays a huge role in engine performance, without a doubt. Way back in 1997 Foggy’s bike was running the two-injector setup on his 996. The factory ran a set of 60mm throttle bodies, really they had a number of different diameters to select from depending on the track, and tuning of the bike. A single injectors operated at low to mid-range rpm, these where the forerunners the 996 dual injector setup. The special second injector fed a brass tube that was bent over the top of the velocity stack. At high rpm the P8 ECU would fire the second injector, it then would spray an better-atomized fuel pattern into the motor allowing it to make better peak horsepower.

The finer the pattern of fuel, or better the fuel is atomized, the bigger the bang you get when the fuel charge is lit. With the stock 996, giving two injectors different airflow velocities doesn’t make for proper fuel atomization during part throttle settings. This is what the stock dual injector setup does, with one injector getting an almost smooth unimpeded airflow, while the other gets turbulent air at part throttle. All due to the injector location beneath the butterfly valve of the throttle body. How would you minimize this? Dump the fuel farther above the throttle body butterfly valve. Atomize it well before the butterfly valve. And we wonder why the single injector works so well on our dual injector bikes. It makes fuel atomization consistent. Don’t believe me. Ride a 996SPS with a P8 ECU with a sequential injector setup! The second injector fires at around 6-7 thousand-rpm, giving the motor proper and consistence fuel atomization when the butterfly valve is parallel to the throttle body and the second injector is firing at wide open throttle.

Also, working with the 748R injectors is a tough way to make horsepower as they have the WSS restrictor cast into them! Why not go with the 998/999 showers if you’re building a liter motor? The 998/999 showers are open and free of the WSS restriction. You just need to make sure the rest of the motor is up to their flow rates.

Brads right! If the factory can make a brass tube work, then having a factory shower system should be a piece of cake for the right tuner. Sniff the pipe and add or sub-tracking fuel where its needed. It would be much easier to tune the factory dual injectors as chips are available. Also, built motors will have specific ignition needs as well. A PC won’t address this area either.



I vote for the showers!

You’ll never realize the full potential of your bike as long as it remains on the island. It needs to spend some quality time with an experienced Ducati tuner for the setup you have. Only then will you realize the sum of all your efforts.

 

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the factory went to shower injectors for a reason - ie, it works. the first production bike they appeared on was the model with the most demands placed on it - the supersport bike. the jap 4s are just so fast that ducati really had to use all their race experience to produce a homologated base model that could realistically win with the allowed mods. and it was still too slow and heavy.

the first time i rode a 748r i was amazed it ran so well down low. the 749 and 999 run very well considering they have fuel sitting on the butterfly and dribbling past it at low throttle.

the first bike i saw showers on was the '98 triple injector bikes ddt were running - the normal dual injector style throttles with a shower above. they were running motec on them from memory and could vary the point at which they switched from the duals below to the shower above. i was told that, after they managed to ask the factory guys the right questions (they wouldn't tell them stuff straight up, but would answer questions) they found quite a bit more power in the midrange going to the showers earlier.

i don't think it will really make much difference to what you're trying to acheive. you can easily machine the 748r throttles to give a nice taper out to the bottom. you certainly won't lose anything by running them, but being the tightarse i am i wouldn't do it for the sake of it. i'd be tuning it with the std throttle bodies and then going up if i felt it was cost worthwhile. remember there's a big difference between a 999F making 180hp and a 996 making 130hp. that's realistically a huge airflow difference.

you can machine the normal 50mm throttles out to 54mm if you want, and can make a shower setup pretty easy too. nothing too hard about it, altho running them as sequential with a 1.6m is not possible.

without meaning to sound like a condescending prick i think there's a few guys here throwing money at parts (tuning bling?) that would be better spent on basic tuning of what is already there. the iwp 069 flow quite a lot more fuel than a green side flow injector, but that's just a overall fuel adjustment. and the big throttles flow more air at smaller throttle openings, again a basic fuel adjustment.

if you're running g cams i can see no real reason why you need a big throttle. there's so much time for air to get in with that much duration that it may be better served by a smaller inlet system aimed at exploiting the charge velocity. the g inlet has 44 degrees more inlet duration than the 748r inlet, and 48 more than the 998s inlet.
 

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Discussion Starter · #8 ·
Now this is the discussion I was hoping for.

The only draw back I can see with the shower injector's is at Idle and low RPM’s do to the butterfly valves position. Sense the injector's are above the butterfly valves, the injectors shoot against the valve and the fuel more or less drips down the intake. On a race bike it won’t really be an issue but on a street bike I could see some problems.



Now about my bike. I started this project about a year and a half ago. The reason I went with the 748R injector's is because that's what was on E-bay at the time. I got the injectors, intakes, and the air box for $500.00... I couldn't pass it up. I posted my plans almost a year ago, and honestly I didn't get much help. I figured know one has really tried it. Once my race bike had some down time, I started to change everything over. The first thing I learned was the valve covers on the intake side are different. No big deal, I made a new set, and they work perfectly. Now I knew the 748R frame were a little different, I just didn't know what part. I found out when I was trying to install the lower section of the Air box, so I did a little math, and made a new one that would fit (not to toot my own horn, but I'm dangerously good at fabricating parts). After everything was bolted on I just had to figure out the electrical side. I sent the ECU to Bruce at BCM Ducati, and they did there thing to it. Once everything was put together I ran it on the Dyno, and faxed a copy of the results to BCM. They asked what I had my fuel pressure set at and if I have bored TB's. Well for some reason I forgot about that part, which is a big bust on me considering my background. I bored the restrictor's out on the TB's in accordance with the spects BCM gave me and bored the intakes to match the ports on the heads and the TB's. And bump the fuel pressure up. I play with the fuel pressure, Idle, and trim until I found the sweet spot.

The bike runs a little rich over all (better safe then sorry), especially at idle. And at 4,500 to 5000 RPM the bike is AFU, but from then on it’s an untamed beast.



I agree I can not unleash the bikes full potential while it’s on this Island, but I will try to get as close as possible with what I have to work with.
 

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I say if you have the time, patience and $$$ keep going for your goal. There is something very satisfying about acomplishing things like you are doing:twocents
 

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This is all good stuff!

Out of interest, when you guys are boring the 748R TBs are you only taper boring to remove the FIM restrictor or are you also increasing the overall diameter?

If you're increasing the diameter what effect will this have on charge speed? Slower, yes? Reason I pose the question is that I've been told that over the last couple of years the factory race bikes have actually had material added to the inlets to increase the charge speed - I guess this is so you can pack more charge in for any given valve open duration. Does faster mean denser and better burning?

I'm just about to have my TBs bored so any input would be much appreciated.

Thanks, Neil.

P.S. Please ignore the piss-poor terminology! :wtf
 

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the tb mod is simply a tapered bore to remove the step restrictor. iirc, there's no actual increase in the final diameter where the tb meets the head.

the theory of adding material to the intake ports is performed much closer to the valves. therefor i don't think boring the tb's will have the effect of losing intake velocity like you could if you overport the inlets at (closer to) the valves.

i'm no expert though!!!
 

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Discussion Starter · #12 ·
Yes. We are just taper boring the restrictors out. But in the process the Diameter at the very bottom of the throttle bodies may be increased by a few thousands. And I don't think I'm smart enough to answer your question about charge speed, but I'll give it the old' collage try.
I think your talking about the Venturi principle when you asked about charge speed. Which states that gas or liquid that’s flowing through a narrowed down section (A VENTURI) of a passage will increase in speed and decrease in pressure compared to the speed and pressure in the wider section of the passage way.
In my humble opinion any sharp bends, ledges, or a real shape narrowing like the restrictor we’re talking about is a bad thing in the intake. What I am doing is giving the air a smooth flowing passageway to flow through. Remember not to make it to smooth, you want the walls to be a little rough (turbulent air on the walls is a good thing). If you have a stock 748R I don't think you would notice any real gains by boring the TB's, But in all honesty I would do it just for G.P. But I'm no expert either.

 

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Another point

Just some input here. I had the chance to talk with John Hackett of JHP about boring my 50mm throttle bodies to 54mm. The bike is a Guy Martin (mbp) built 1036 that started out as a 2000 996. I thought the 54 mm throttle bodies would be an overall improvement, but was told no. I was told by John that the bike would not run as well through out the rev range with the 54's. In addition the gain on top would be minimal. This is a pure track bike and even then both John and Guy convinced me to not do the 54mm mod. Keep in mind this is not a tuning issue as the bike has a custom map now and would have another made with any further mods. I am not an expert, but they are. Of course you can map and tune to make most anything work. It goes back to brad black's phrase "tuning bling", would they a be an improvement in the real world where most of us ride from about 3000 to 9000 rpm on these bikes with most of the time spent around 5000 to 8000 rpm, I think they are not an improvement there. Perhaps on a full race bike run at the top of the rev range most of the time, and rebuilt every 500 km, yes, but for my money, no.
 

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duc1036 said:
...Perhaps on a full race bike run at the top of the rev range most of the time, and rebuilt every 500 km, yes, but for my money, no.
what money? it's a little to no-cost mod depending on your resources.

i can't comment on your tb's but for the 748r style i don't see how boring them to remove the step restrictor could adversely affect performance. all that's being done is a smoothing out of the taper.
 

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Discussion Starter · #17 ·
I am now convinced that the installing bored 748R TB's and a modified air box on my 996 was a great Idea. Sense I installed a fuel pressure regulator and set it at 58psi, I didn't have any problems with power at todays race . I think combined with engine work this is an awesome setup. and I only have about $600.00 bucks invested in parts and materials. I plan to run it on the dyno again to what kind of gain I have. Before the bore and with stock fuel pressure I had 127rwhp with 73tq, and the bike feel much more powerful now so I can't wait to see the gains. I will post it as soon as it's done.
 

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I heard from a fellow ducatista that JHP said that the bike would not run properly with 54 tb. I don't see why though, mine is just fine I think. Check the torque curve out, not lacking bottom and mid I think http://www.yellowtree.se/upload/file/SLO_Torque_Fuel.jpg. However it would be intresting to get out of the guessing and mount the original and dyno it to see if and what it does in power.

Here's what epicycle got: http://www.epicycle.com.au/graphs.htm play with the interactive graph.
 

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My money

chiromikey said:
what money? it's a little to no-cost mod depending on your resources.

i can't comment on your tb's but for the 748r style i don't see how boring them to remove the step restrictor could adversely affect performance. all that's being done is a smoothing out of the taper.
I was not commenting on the removal of the step in the 784R bodies. I was addressing the 50mm to 54mm dual injectors on the 996 type bikes. Removal of the step inside the 748R bodies and smoothing them out is a great idea. As far as other set ups like I said you can make anything work, almost, ask Doug Lofgren. There are those that favor the single injector mod also. Lots of solutions to the same problem. As far as little to no cost I disagree. You have the mod to the throttle bodies, which in the scheme of things might not cost that much, but the additional cost to set them up with a custom map and dyno runs can start to add up. Also I do not think that the removal of the step in the 748R bodies brings them to 54mm, but to 50mm. It is also a sort of apples to oranges comparison, shower injectors to dual non-shower injectors, 50mm to 54mm so forth.
 

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Torque curve

TomTom said:
I heard from a fellow ducatista that JHP said that the bike would not run properly with 54 tb. I don't see why though, mine is just fine I think. Check the torque curve out, not lacking bottom and mid I think http://www.yellowtree.se/upload/file/SLO_Torque_Fuel.jpg. However it would be intresting to get out of the guessing and mount the original and dyno it to see if and what it does in power.

Here's what epicycle got: http://www.epicycle.com.au/graphs.htm play with the interactive graph.
I think what might be the negative, if there is one, to the 54mm mod looking at the graph is the curve from 4000 to about 6000. In particular the dip right at 5000. The numbers look good of course, but they are relative to the dyno run and type of dyno, the curve is the most important. Just my thoughts of course. As in my previous post if the bike were always in the 6000 to 9500 rpm range then the curve is real flat. I find myself in the 4500 to 6000 range a lot, so for me I want that rpm range as flat a torque curve as possible with no dips.
 
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