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I'm interested in this mod:
You can modify the pressure regulator. Take a look at the fuel panel pics. in our tech album. It's the thingy on the right.

Remove that and you can see that it has a flange and an indent in the top of what I call the hat. That's were the spring is. Get a large socket to support the unit on the outer flange and a smaller one to match the indent on the top of the hat.

This is where the rocket science and engineering come into play so pay attention :razz:

You put the regulator with sockets into a vise and squeeze a bit so the socket that's in the indent makes a deeper indent. How much? Using the the engineering term, TAR. (That's About Right)

This will make Dan'l freak and geek :razz:

This is why I am going to make some pics and using a depth mic. take some measurements of a stock one comparing to a modified one.

What you are doing is adding pre load to the spring underneath the hat changing the psi from the stock 40 to about 50 or 60 psi.

What this does is to enrichen the F/A ratio per injector shot across the board of the current map. In addition to a superior driveability and much crisper throttle response I have seen my MPG get more stable and even a bit better that before. It looks like the added pressure aids in the spray pattern from the injector. (Last little 200 mile trip loafing along I got 56.7 mpg.

I'd still advise getting another regulator to modify. They are easy to come by.

I see this as no different than changing the jetting on the carbed. twins to get a better running engine.

Don
Who has done it and what were the results particularly long term? Is this for all Sprints or certain year/models?

Hi Martin and all. Just take a peep at the upper right of our panel here. You'll see Album. Just click on the clicky and it will take you to the Sprint Tech album.

Don
I've looked around and can't find the Sprint Tech Album. Does it still exist?

TIA

-Mike
 

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I've never managed to find said tech album so I'm thinking that it's no longer there.

I'm not too sure if this mod is still done, it's well old school and low tech. If you were going to mod the fueling you'd probably be best advised doing something with tuneECU, where you can do controll, and more importantly, reverse your changes.

Would you hit your laptop to make it go faster?
 

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Hitting your laptop to make it go faster wouldn't work, whereas tweaking the FPR does increase the pressure. That said, though, I haven't done the FPR mod precisely because it's not reversible. (And just yesterday, I did the linkageless shifter mod and had need to reverse it.)

Cheers,
-Kit
 

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As a fan of the FPR Mod, let me offer this:

The "Fuel Pressure Regulator Modification" applies to the 955 bikes. I've never heard of a 1050 needing it, and the procedure would be a lot more involved.

The mod involves the (one-time) depression of the top of the regulator to add spring pressure inside the regulator. This has the effect of raising the stock 40-ish psi fuel pressure to around 60psi. (I base these numbers on observations of the Mod being performed at a Dealership on a 955 Daytona.)

The added pressure has no perceived negative effect on the fuel system. The improvements include:
quicker starting,
'crisper' response to changes in throttle settings,
better fuel economy (not significant, but I saw roughly 7 more miles per tank), and
it cures the annoying 'strangling squirrel' sound when the bike is first turned on.

The changes are immediate, and permanent.

I used the 'Adventurer' method to do the Mod. As in, I didn't remove the regulator from the bike.

Do a search for FPR Mod. Several posts on the topic over the years.
 

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I've done it. I like it. It smooths low rpm out, no hesitation/surge at 3000 rpm. Just feels really good. Pulls like a train. You can't do it on a 1050 bike, the fuel pressure regulation is entirely different than the 955 bikes.
 

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...it's well old school and low tech. If you were going to mod the fueling you'd probably be best advised doing something with tuneECU....
The fuel pressure mod is based on sound concepts. The smaller and more uniform the fuel droplets in the mixture are, the more rapidly and completely the fuel will burn. Depending on the injector design, raising the fuel pressure MAY reduce droplet size, improve the injector spray pattern, or both. Anecdotal evidence here on the forum seems to indicate that such improvements result from the FPR mod.

I haven't done it because I think it would be preferable to use more modern, director plate injectors to get an improvement in mixture quality. That involves buildinng a new fuel rail, sourcing appropriate injectors, replacing all the fuel system plumbing, and re-tuning the engine on a dyno to quantify the results. I'm pursuing that, but I'm not there yet.
 

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I've had this on my scooter since my dealer did it at the first 500 mile check using a cast off noisy FPR. Back then there were customer complaints of noisy FPR's and if asked the dealer would change them out free gratis. Nothing wrong with them, they just made a lot of noise. I got that for free and still have the unmoded FPR that came on the bike.

Old school? Old tech? BLAH! It works and if one thinks about what's happening you'll see that it an extremely cheap and effective way to deal with an overall lean condition which is what the 955's deal with.
1. You can't increase FP with Tune ECU, that's a mechanical function.
2. It's always easier to tune down from excess than try to tune up from a deficit.
3. More FP gives a harder shot with better atomization of the fuel droplet size. Smaller size = better light off and more efficient burning of the fuel without a tendency for the fuel to puddle.
4. This doesn't change the mapping it just brings the fuel to air ratio slightly above the ideal 14:1 so then with your Tune ECU you can trim the mapping back a bit to ideal instead of adding a longer shot duration to do the same thing there by decreasing fuel mileage.

There are no down sides to this what so ever.

I've known guys with blower bikes and a 955 Daytona running at the Salt Flats use this same mod, only they are modding to about 100 psi.

Yes, it is reversible. Just put in a stock FPR. But I guarantee you won't even think about it after it's done.

It's a very simple procedure not warranting the time to photograph the whole thing. Just remove the FPR. A 6mm socket fits in the dimple of the FPR hat spring side. Get another socket that fits the brim of the hat (collar). Chuck into a vise and squeeze a bit. How many inch lbs. or thousands ????Beats me, this is hotrodding and not rocket science.

It's difficult to say what caused what but at that same time we put on an 18 in front but afterwards my bike went from an average of 46 mpg to an average of 51. Acceleration was much smoother and responsive. My thinking is that the better fuel delivery allows less throttle application for any given positive throttle application. Meaning it takes less throttle opening to get the desired result.

What it won't do is to give appreciable HP increase. You get higher HP with leaner settings. It will "feel" like more as the lean bogs and holes in the curve are filled up.

That's about it. If you don't feel you are comfortable doing this, then don't but it's a far better way to dial in more fuel that to keep trimming fatter.

Don

ps, Sometimes it's the low-tech simple ways that us old farts understand that still give better results.
 

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Once upon a time i was convinced, now once again. Just had the tank off and on, and off and on and off and on again, and I did have the temptation.
 

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Looks like you moved it a bit. How does it feel? Did you get rid of that bottom end snatchyness?
 

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To answer this correctly I need to know the brand hammer used and the exact weight.

Also the exact time (this must be converted to Australian Eastern Std time you realise), and if you had your mouth open when you swung the hammer.

Other variables are what the tides were and the position of the moon in relation to the sun.


Other wise in my non expert opinion that looks ok to me mate.:thumb


Of course you do realise I am not a mechanic, not very technical and I have never done that mod don't you?:knockknock

DaveM:Group
 

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I just got back from a ride. My first impression was that nothing changed, however with a little time doing parking lot maneuvers, I noticed the low revs were smoother, maybe a tiny bit more torque or at least smoother delivery. My butt-dyno says no change to the peak power as I tested running WOT through the first two-and-a-half gears a few times.

I also did my first back-to-back test comparing the Sargent seat to the stock seat. Does anyone want to buy a stock seat?
 

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I did the FPR mod this morning on my '04. A previous post said to go 3mm depression,so I used that as a guide. I used a ball bearing instead of a socket, better fit. I went down 1.75mm and stopped there (it will be very easy to go down further--not so easy to undo a mistake here. I measured this with a digital caliper, something every home mechanic should have. (Harbor Freight has them for as little as $20, and they will do fine for this type work,once you have one you will be suprised at how often you use it). There was a noticable improvement. After 40K miles I think my FPR may have been getting a little lazy. Bottom end is crisper now, and very nice improvement in top gear roll on from 60 to 100 MPH.
 

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So, did you take it out to do this or leave it in place and if it's to be taken out does the gasket need replaced?
 

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So, did you take it out to do this or leave it in place and if it's to be taken out does the gasket need replaced?
It has o-rings. So if they are in good shape, just lube them, and reinstall.
Use internal snap ring pliers to remove the retaining clip, then ease the FPR out of it's nest.
 
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