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[Black Diamond]

Since I seem to have a problem with just leaving well enough alone with my SERK4, I got a wild hair up my ace and sent my stock 50mm throttle body to Horse Power Inc. They ported and polished the throttle body to 54mm.

The attached pic is the throttle body stock.

[Black Diamond]

This is how she looks after HPI worked on it.

[Black Diamond]

I had the shop remove my 58mm SE TB and replace it with the HD/HPI 54mm. After very little tuning, I have virtually the same tq curve and hp line as before. I did not get a copy of the graph as we are just getting started on this experiment.

Couple of advantages to the 54mm:

-Uses the stage 1 A/C mounting plate after it's opened up a bit (the 58mm requires a seperate mounting bracket and a/c filter) SE / Big Sucker etc.

-Allows the use of the SE/KN 3 hole A/C filter (the 58mm is a 4 hole design that only HD offers a replacement for)

-The throttle body is shorter than the 58mm allowing the right knee/foot to be in a more natural position

-Modification is cheaper ($250) than the 58mm tb ($399.95) with related parts ($149.95 mounting/breather kit)

-MPG went up about 2 mpg on the highway to 41 mpg steady.

I am using the high flow injectors in the 54mm which I had removed from the 58mm. My 58mm is not stock as it was ported and polished by Wes @ Cyclerama. TR looked at it when they were dynoing my bike and remarked Wes had done a very good job on it.

This winter, as the riding season will be over up here, I'm planning on making several comparision runs to see what more we may gain and which tb will be best for my build. As I said, I just can't leave well enough alone. Besides, they give you a neat looking little HPI knob on it. LOL

JW

[SBB]

Jeff

In order for HPI to modify my 50MM T/B I have to have one.

I do now, same scenario as you.

I will be very interested in your results.

Good luck, where you lead I may follow.

                  


SBB

[Black Diamond]

That's what this great site has done for me so many times I just wanted to give something back if I can.

JW

[jfh]

JW,
Looking forward to your testing results. I an currently running the 58mm SE TB, but suspect it is not performing as well as the HPI 54mm.

Just curious, any data on the improvements obtained on the SE 58mm from Wes' port and polish?

Thanks,
John

[FNGw/08SERK]

Very interesting Jeff ... let us know what you find. It has been suggested by Joe at http://www.joescyclerepair.com/ to supersize the TB up from 50 to 58mm. Didn't discuss this option. Will anxiously await the results. Brian doin all the tuning??

Howie

[Wildrat]

Looks like something a good DIY'r could do at home. Interesting!

[Heatwave]

I had the shop remove my 58mm SE TB and replace it with the HD/HPI 54mm. After very little tuning, I have virtually the same tq curve and hp line as before. I did not get a copy of the graph as we are just getting started on this experiment.

Couple of advantages to the 54mm:

-Uses the stage 1 A/C mounting plate after it's opened up a bit (the 58mm requires a seperate mounting bracket and a/c filter) SE / Big Sucker etc.

-Allows the use of the SE/KN 3 hole A/C filter (the 58mm is a 4 hole design that only HD offers a replacement for)

-The throttle body is shorter than the 58mm allowing the right knee/foot to be in a more natural position

-Modification is cheaper ($250) than the 58mm tb ($399.95) with related parts ($149.95 mounting/breather kit)

-MPG went up about 2 mpg on the highway to 41 mpg steady.

I am using the high flow injectors in the 54mm which I had removed from the 58mm. My 58mm is not stock as it was ported and polished by Wes @ Cyclerama. TR looked at it when they were dynoing my bike and remarked Wes had done a very good job on it.

This winter, as the riding season will be over up here, I'm planning on making several comparision runs to see what more we may gain and which tb will be best for my build. As I said, I just can't leave well enough alone. Besides, they give you a neat looking little HPI knob on it. LOL

JW

So if I understand correctly the dyno performance is the same with the HD 58mm TB as it is after porting/polishing the stock 50mm TB (upto 54mm). I'd like to see the dyno that confirms that.

One advantage you didn't note if you're using the 58mm TB is that you can then sell your original 50mm TB. They are selling for over $300 on Ebay.

[Black Diamond]

JW,
Looking forward to your testing results. I an currently running the 58mm SE TB, but suspect it is not performing as well as the HPI 54mm.

Just curious, any data on the improvements obtained on the SE 58mm from Wes' port and polish?

Thanks,
John

Hi John

I do not have any data on how much Wes improved the SE 58mm. He ported and polished it before I ever used it. He remarked the SE 58mm flowed ok but was looking forward to the aftermarket coming out with something better.

JW

[Black Diamond]

Very interesting Jeff ... let us know what you find. It has been suggested by Joe at http://www.joescyclerepair.com/ to supersize the TB up from 50 to 58mm. Didn't discuss this option. Will anxiously await the results. Brian doin all the tuning??

Howie

Hey Howie

HPI said 54mm was a large as they could open up the stock TB. The only changes to Brian's tune was done at the top end. Actually took some fuel away to keep it in line with his tune. This was a quick turn around switch as I was on the road again. I hope to wring it out over the winter as we don't have much motorcycling in Dec - Feb. LOL.

My tuner is going to T-Man's for their tuner class soon.

JW

[FNGw/08SERK]

Hey Howie

HPI said 54mm was a large as they could open up the stock TB. The only changes to Brian's tune was done at the top end. Actually took some fuel away to keep it in line with his tune. This was a quick turn around switch as I was on the road again. I hope to wring it out over the winter as we don't have much motorcycling in Dec - Feb. LOL.

My tuner is going to T-Man's for their tuner class soon.

JW

MPG improvements aside .... any noticeable difference from the saddle??

[Black Diamond]

So if I understand correctly the dyno performance is the same with the HD 58mm TB as it is after porting/polishing the stock 50mm TB (upto 54mm). I'd like to see the dyno that confirms that.

One advantage you didn't note if you're using the 58mm TB is that you can then sell your original 50mm TB. They are selling for over $300 on Ebay.

For my build, I am getting virtually the same results SE 58mm TB ported and polished vs the HD/HPI 54mm TB using the same high flow (5.3) injectors. I am not saying this will be true in all cases. As I posted earlier I do not have the d sheet on this however, I may pick one up in the near future and will share it. As you know, we are extremely limited in our choices at this time. I just wanted to play with this to see if I'm getting all I can from my build. Not saying anyone else should toss their SE 58mm based on my experience. Just want to share what we're seeing.

You are correct, as with any part, eBay is the place to try to recoup some of your investment. After our testing I will be selling one or the other.

JW

[Fullsac Performance]

Hey Howie

HPI said 54mm was a large as they could open up the stock TB. The only changes to Brian's tune was done at the top end. Actually took some fuel away to keep it in line with his tune. This was a quick turn around switch as I was on the road again. I hope to wring it out over the winter as we don't have much motorcycling in Dec - Feb. LOL.

My tuner is going to T-Man's for their tuner class soon.

JW
[/quote 

Its seems odd at first, but a larger TB will indeed send the existing tune to the rich side. The MAP sensor sees more KPA or less vaccum at the same throttle position.
The computer responds with more fuel.

Anybody have a 50mm FBW TB for sale, I'm interested. Sounds like an interesting dyno test.

Steve George

[Black Diamond]

MPG improvements aside .... any noticeable difference from the saddle??

Nothing I can put my finger on. With my short legs, just bringing my knee in more was worth it so far. For someone like you brother, no biggie.

JW