HarleyTechTalk

Technical Forums => Twin Cam => Topic started by: Matty_d on March 11, 2020, 06:35:36 AM

Title: Question about throttle bodies
Post by: Matty_d on March 11, 2020, 06:35:36 AM
Here is my current build.
2009 FLHTCU, 107 CI,
Suburban Speed pistons 4.4cc
S&S 91cc heads milled to set 10.8 comp,
T-Man 5902PS cams
SE 58mm TB 5.8 injectors
Stock Catless headpipe, Supertrap slipons
Power Vision and Target Tune

Now my question is, would my lower end RPM be better with the stock 50mm TB and stock injectors? The bike is kind of a dog till it hits roughly 3200rpm. I know the intake ports are larger on the heads than the 50mm tb. Would that cause an issue?

Title: Re: Question about throttle bodies
Post by: lonewolf on March 11, 2020, 06:54:46 AM
Quote from: Matty_d on March 11, 2020, 06:35:36 AM
Now my question is, would my lower end RPM be better with the stock 50mm TB and stock injectors?

No, if tuned properly
Title: Re: Question about throttle bodies
Post by: rigidthumper on March 11, 2020, 07:09:06 AM
Short answer? No.
Have you had it on a drum to see where you are at? That combo should peak near 120ish, if allowed to breathe. A D&D Fatcat or Dragula would help tremendously. If you want quiet, find a set of Crusher Mellows and match them to a Fullsac DX headpipe.
Title: Re: Question about throttle bodies
Post by: Matty_d on March 11, 2020, 07:23:03 AM
I have had it on the dyno. Not happy with the results.

[attach=0]
Title: Re: Question about throttle bodies
Post by: rigidthumper on March 11, 2020, 07:34:21 AM
A cam change would pick up the left side, at the expense of the right. How much time do you spend at/above 5500?
Title: Re: Question about throttle bodies
Post by: Matty_d on March 11, 2020, 07:40:43 AM
Quote from: rigidthumper on March 11, 2020, 07:34:21 AM
A cam change would pick up the left side, at the expense of the right. How much time do you spend at/above 5500?

Might hit 5500 once and a while, but not very often.
Title: Re: Question about throttle bodies
Post by: Coyote on March 11, 2020, 07:47:32 AM
Did you tune the number of discs on the Trapp?

Your build is pretty close to mine although mine was a 113"

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Title: Re: Question about throttle bodies
Post by: Matty_d on March 11, 2020, 07:55:53 AM
Quote from: Coyote on March 11, 2020, 07:47:32 AM
Did you tune the number of discs on the Trapp?


There are no discs on these slip ons. I don't know which ones they are but I know they are from 2009.

I know I need a better tune but want to make sure things are right before I look for a better tuner.
Title: Re: Question about throttle bodies
Post by: Coyote on March 11, 2020, 08:07:20 AM
The 590 does lean to the right but I suspect you also have a tuning issue.  I have no idea about your exhaust setup. I'm sure some of the tuners here would know better.
Title: Re: Question about throttle bodies
Post by: No Cents on March 11, 2020, 04:37:46 PM
  you have the wrong cam choice...if you wanted more off the bottom. The exhaust pipe is also a major player in the game.
The SE 58 and injectors should be perfect for your build.
Title: Re: Question about throttle bodies
Post by: Barrett on March 11, 2020, 05:00:01 PM
If your gear ratio is like my 08 fxdf @2.79:1 regearing would be a good option
Title: Re: Question about throttle bodies
Post by: TorQuePimp on March 11, 2020, 09:02:00 PM
I've had more than one build on that Dyno...... middle of the road imo

I would confirm you have 10.8:1 first

Agree with Robin......should be minimum high teens to 120 horse....tq depending on pipe should be close to 120

The tb is not hurting you at all.......stock 08 tbw to Hpi 58 is +24 cfm and 6 feet per second different......leave that alone

Title: Re: Question about throttle bodies
Post by: Deye76 on March 12, 2020, 06:30:19 AM
"I've had more than one build on that Dyno...... middle of the road imo"

Agree, had my 2004 RG on that drum, came away spark knocking, took it back, only slightly better. Wasn't the build, as I took it to another tuner, ran great.
Title: Re: Question about throttle bodies
Post by: ThumperDeuce on March 12, 2020, 06:14:41 PM
My 107" build made 100lbft at 2k with a Wood 400G and some head work by UnderGround Heads.
Title: Re: Question about throttle bodies
Post by: doctorevil on March 12, 2020, 07:09:14 PM
coyote what pipe on that dyno graph? I have same build as you difference from yours woods777 branch heads red thunder pipe almost identical graph torque a little to the left. :up:
Title: Re: Question about throttle bodies
Post by: sfmichael on March 12, 2020, 07:45:59 PM
Quote from: Coyote on March 11, 2020, 07:47:32 AM
Did you tune the number of discs on the Trapp?

Your build is pretty close to mine although mine was a 113"

[attach=0,msg1336599]

getting ready to build a 110 with the 590 but am definitely interested in low end torque
do you feel it's not a good cam for that?
Title: Re: Question about throttle bodies
Post by: kd on March 12, 2020, 07:53:40 PM
Depends on your compression and gearing.  The compression feeds early torque and the gearing tricks into showing up even earlier. More compression may require a tighter quench, compression releases and a good tune.  The lower gearing (surprisingly) may give you better mileage.
Title: Re: Question about throttle bodies
Post by: sfmichael on March 12, 2020, 07:59:17 PM
I'll squeeze it as hard as possible but I'm @ 6000' and even if I build it to have 210-215 ccp @ sea level I'll be below 200 here
Title: Re: Question about throttle bodies
Post by: Matty_d on March 16, 2020, 04:43:54 PM
Well, going to have to have a word with my guy at Suburban. Did a compression test today and am only at 185psi.
Title: Re: Question about throttle bodies
Post by: kd on March 16, 2020, 05:05:07 PM
Check it with another "known" to be good gauge first.  Compression tester gauges seem to be all over the map.
Title: Re: Question about throttle bodies
Post by: Matty_d on March 16, 2020, 05:13:00 PM
Quote from: kd on March 16, 2020, 05:05:07 PM
Check it with another "known" to be good gauge first.  Compression tester gauges seem to be all over the map.
Agreed, but I looked and the invoice from the build and they put in a 0.04" head gasket instead of 0.03". I was told he was going to mill the heads and set it up for 10.8:1.
Title: Re: Question about throttle bodies
Post by: Matty_d on March 17, 2020, 11:12:52 AM
Spoke with the guy that built the engine. Confirmed some details of the build. Heads are at 84.6cc. Front and rear pistons are both 0.006" in the hole. So with the 0.04" head gasket, that puts the compression mathematically at 10.77:1. and 201.2ccp. Taking it back to him to have him do a ccp and leak down test on to. Also going to put it back on the dyno to work on the low end.