TQ loss w/Thunderheader & stage 1 : V-Twin Forum: Harley Davidson Forums

bluelab · 12-04-2005, 01:15 AM

I have been thinking of putting a Thunderheader / Powercommander / Ness Big Sucker on my stock 05 FLHTI. I talked to a tuner today about this set up; he said that the TH is a drag pipe designed to produce power at high RPM's and I'll lose TQ at the low rpm's (below 3000). Is this true? I love the TH sound, but don't want the tq loss.

-bluelab

Ozzie In Arabia · 12-04-2005, 02:08 AM

Quote:

Originally Posted by bluelab

I have been thinking of putting a Thunderheader / Powercommander / Ness Big Sucker on my stock 05 FLHTI. I talked to a tuner today about this set up; he said that the TH is a drag pipe designed to produce power at high RPM's and I'll lose TQ at the low rpm's (below 3000). Is this true? I love the TH sound, but don't want the tq loss.

-bluelab

Go some where else..............too many guys on here having the best performance with the T Header.

Nothing wrong with the Big Sucker but Doherty Power PACC is on sale at the moment.......also an excellent A/Cleaner.

I have actual flow numbers for this unit from one of the members here that is experimenting with some changes to his bike and heads and the Doherty Power Pacc did not effect the airflow what so ever..............so in my mind is quite a good unit.

All the best, Ozzie

csoday · 12-04-2005, 02:50 AM

Quote:

Originally Posted by bluelab

I have been thinking of putting a Thunderheader / Powercommander / Ness Big Sucker on my stock 05 FLHTI. I talked to a tuner today about this set up; he said that the TH is a drag pipe designed to produce power at high RPM's and I'll lose TQ at the low rpm's (below 3000). Is this true? I love the TH sound, but don't want the tq loss.

-bluelab

He's an idiot, stay away

Belicoso_Fino · 12-04-2005, 08:04 AM

Quote:

Originally Posted by csoday

He's an idiot, stay away

What he said. The Thunderheader is NOT a drag pipe, although your "tuner" may be smoking one.

bluelab · 12-04-2005, 08:42 AM

Well, this tuner said the TH was designed for racing applications, meaning it's a high flow pipe for big motors. I don't know the guy ... just a talking at his shop.

I've heard about a torque dip in thunderheaders from several tuners in my area. Have also read on this board that these pipes can over-scavange 95" builds, and that modifactions to the pipe (though minor) are needed to correct this.

My bike is stock, and I'd like to add just the TH, AC and powercommder. I really don't want to get the bike on a dyno, find a torque dip below 3000 rpm and be unable to tune it out.

Seems like every tuner I talk to has a different opinion about pipes. WTF?
I'm still leaning toward the TH ... just want to be damn sure it's the right pipe.

Thanks again

-bluelab

GRock · 12-04-2005, 09:04 AM

Glad to see you stick to your guns, bluelab!

The Thunderheader is absolutely a much better performer in high output engines and can, and will, cause a torque dip on mild or stock engines because of overscavenging; especially on the front cylinder. With all due respect to Ozzie, Chuck, and Bella Lagosi, the pipe is NOT a drag pipe but your tuner has legitimate concerns IF he doesn't know how to cure the problems. The stock cam simply does not have enough lift and duration to allow the TH to do it's thing and your EFI system will have problems dumping enough fuel into the cylinders to compensate for the TH high scavenge rate. Stock heads also greatly limit the ability of the TH to perform. However you will see gains due to the combination of the AC AND the TH, although your bottom end will see little to none, and you high end the same as the bike will simply run out of breath as the TH will be sucking on a closed straw. So midrange is left and that is where you ride so there will be gains. What you need is to address the basic cam and head issues and you will already have a nice exhaust set up in place. The TH is a great pipe (top 3 or 4 IMHO) for performance, but you don't have the performance combo yet. And I have been saying this for years, if a tuner doesn't know the inherent issues that come with that pipe and how to tune for them, especially on a stock build, then your gains are small. Great loss of power in the bottom end?? No! You won't feel it on a stock bike, anyway. But no big gains either! The pipe can be adjusted with both separate cylinder AFR trim and timing AND working the tabs in the baffle to cut down on the scavenging rate. If your tuner doesn't know how to do that (or doesn't want to) then find another tuner, regardless of what pipes you go with.

(Every time Ozzie is on the same thread I tend to write a short story. Now my head hurts!!)

dbrd bank · 12-04-2005, 09:23 AM

GRock, I am considering a similar set up, scratch the PC for a SERT and going with the D&D FatCat. Will I have the same problems? Can I just go with the FatCat first add the SERT and big sucker later? I have an 04 RK with stage 1, AC and Kerker Slip-ons.

Thanks

MaineUltraClassic · 12-04-2005, 09:24 AM

I have a PCIIIusb, Big Sucker, and TH on my '05 FLHTCUI............and I love it.

Before the TH, I had true duals & Wild Pigs.........weird sound and loss of power with true duals.

There is a torque dip with the TH around 2300 rpm........but that is fixable with some bending of the interior baffle at the rear of the TH.

I would say go for it.............if you love the TH sound(which I do too), you can't go wrong with this setup. What small torque you might lose, you will never notice since it will be such a great improvement over the stock set-up.

Steve

GRock · 12-04-2005, 09:53 AM

Quote:

Originally Posted by dbrd bank

GRock, I am considering a similar set up, scratch the PC for a SERT and going with the D&D FatCat. Will I have the same problems? Can I just go with the FatCat first add the SERT and big sucker later? I have an 04 RK with stage 1, AC and Kerker Slip-ons.

Thanks

FatCat kind of has the same tendencies as the TH but for different reasons. It tends to operate better in high RPM's. And really no advantage going to BigSucker over SE AC for your ride. To be honest with you, you will see nominal gains over the Kerker's. And the SERT will get you nothing over what you have now for a basically stock bike.

Look guys, don't get me wrong here. Two into ones are great performers, and SERT's are great tuning modules. But don't beleive all the sales hype. These exhausts and gadgets just can't perform magic all by themselves. You need to put the money into cams and heads for real gains. For stock bikes you will see some gain, which in some cases gets exaggerated by the added sound.

i.e. sounds louder, must be faster!!!

dbrd bank · 12-04-2005, 11:33 AM

So I will get a little boost with the FatCats mostly sound which is alright, the Kerkers are to quite. I was going to do the SERT to get a little better throttle response? also I was concerned I may be running lean with the stage one, the bike pops a little and sometimes will cough when I get on the throttle. My goal was to get some additional power out of the 88 and then go into the motor when I go up to a 95.

GRock · 12-04-2005, 12:08 PM

Quote:

Originally Posted by dbrd bank

So I will get a little boost with the FatCats mostly sound which is alright, the Kerkers are to quite. I was going to do the SERT to get a little better throttle response? also I was concerned I may be running lean with the stage one, the bike pops a little and sometimes will cough when I get on the throttle. My goal was to get some additional power out of the 88 and then go into the motor when I go up to a 95.

If you are going to do more mods later then get the SERT. Thought you said you already had the PowerCommander. If you do, then you can richen up with that and not worry about lean with the Stage I.

MaineUltraClassic · 12-04-2005, 12:21 PM

Quote:

Originally Posted by GRock

And really no advantage going to BigSucker over SE AC for your ride.

The biggest reason to go with the Big Sucker is it is a better design, and cheaper.

The HD SE air cleaner is about $150, the chrome Big Sucker is about $90.

The Big Sucker has all the vent tubes molded into the backing plate, so the install and final appearance is much better. The backing plate is also chrome.....so that adds to the looks too.

Steve

GRock · 12-04-2005, 12:28 PM

Quote:

Originally Posted by MaineUltraClassic

The biggest reason to go with the Big Sucker is it is a better design, and cheaper.

The HD SE air cleaner is about $150, the chrome Big Sucker is about $90.

The Big Sucker has all the vent tubes molded into the backing plate, so the install and final appearance is much better. The backing plate is also chrome.....so that adds to the looks too.

Steve

Agree with you if he didn't already have the AC, but he said he had the stage 1, AC, and Kerkers. So he won't gain anything by swapping out the SE for the Big Sucker.

G

dbrd bank · 12-04-2005, 12:42 PM

No GRock, unfortunately I do not have the PC, I would have to go with the SERT due to warantee issues. Think your right about the big sucker as far a performance goes. Am I right about the popping and coughing?

GRock · 12-04-2005, 03:42 PM

Quote:

Originally Posted by dbrd bank

No GRock, unfortunately I do not have the PC, I would have to go with the SERT due to warantee issues. Think your right about the big sucker as far a performance goes. Am I right about the popping and coughing?

There is no doubt you are running lean. The stage one download is lean even for SE pipes. With the Kerkers, more so. And a two into one will have you into the high 15's for AFR on certain parts of the map. Way too lean.
Decel pop and cough are an indicator. You need to add fuel for cooler running and better power.