Delkevic Header - Yamaha FJR Forum : Yamaha FJR Owners Forums
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post #1 of 7 (permalink) Old 07-18-2020, 01:17 AM Thread Starter
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Has anyone installed the cat-less Delkevic headers?

https://www.amazon.com/Delkevic-Head.../dp/B07H9HH631

I have Ivans ecu flash and Beowulf slip ons. Wondering if I could gain a few more ponies and reduce some weight. Would love to hear from anyone that has installed this header kit.

It looks to be the same diameter as stock unlike the holeshot headers so wouldn't lose any low end torque.

Last edited by RushNatU; 07-18-2020 at 01:22 AM.
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post #2 of 7 (permalink) Old 07-18-2020, 07:23 AM
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I personally say save your money. Nothing much to gain but a lighter wallet. Weight is all down low, you'll never notice. I would keep stock, there is no restriction in them.

What does Delkevic claim as horsepower gain from their dyno testing?
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post #3 of 7 (permalink) Old 07-18-2020, 09:46 AM Thread Starter
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They dont have anything published on their website as far as dyno numbers, or weight savings, but it does “look” lighter, lol.

They do say that fuel remapping is not required.

I would have thought the cats restrict the flow a bit, but sounds like that may not be the case.
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post #4 of 7 (permalink) Old 07-18-2020, 08:00 PM
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Quote:
Originally Posted by RushNatU View Post
They dont have anything published on their website as far as dyno numbers, or weight savings, but it does “look” lighter, lol.

They do say that fuel remapping is not required.

I would have thought the cats restrict the flow a bit, but sounds like that may not be the case.
I just made this exact decision. I chose the 18 inch carbon ovals by themselves and didn’t drop the extra 250 for the full system. Part of this was my e-mails with Delkevic (who are great with responding btw). They told me you could put that full system on the bike with no additional tuning needed, BUT you can’t do any other mods like K&N etc or it will throw a code. This said to me that it likely makes you run pretty lean. That would be my guess. So I opted to do just the pipes first and see about the headers later. As far as weight goes from experience with my VFR the weight savings is in the mufflers... big weight...12+ lbs saved. Headers were only 2-3 going to stainless.

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post #5 of 7 (permalink) Old 07-19-2020, 09:25 AM
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The fact that you don’t need to rejet/remap when adding these systems should tell you all you need to know. It indicates that you’re not increasing the airflow through the engine so no need to add fuel. I would like to see a current fjr dyno sheet with a lambda sensor readout because when I got to spend time on my buddies Dynojet Dyno I was amazed at how rich most bikes ran once on the main circuits, these were mostly but not all carb’d bikes.

It showed me that the internet myth (and it is a myth) that all bikes are delivered from the factory extremely lean for emissions is nothing more than pure bs. Now I will add that most all ran around a 15-1 a/f ratio up to around 2000-2200rpm because that’s where they were required for emissions certification, above 2200rpm they all went pig rich around 10-1 to 10.5-1 a/f ratio, just pig rich which is why you can add a header w/o rejetting them along with the fact that all headers I seen tested made no difference past making more noise. The best you Could hope for was maybe a 2hp or so gain but most made less than the factory stuff, utter waste of money.

Now if you really want to gain some power you need to focus on the intake side as the fjr’s airbox is quite small for a motor of it’s size but be prepared to spend some serious money on dyno time tuning and reflashing things by somebody quite competent. If you just gotta have more power buy something else. My .02

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Last edited by passx; 07-19-2020 at 09:28 AM.
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post #6 of 7 (permalink) Old 07-20-2020, 12:28 AM
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Older carbureted bikes and cars needed to be rejeted etc, newer ones with 02 sensors, computers etc does that automatically. Thatís why nothing has to be recalibrated with aftermarket exhaust.
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post #7 of 7 (permalink) Old 07-20-2020, 08:04 AM
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Originally Posted by G P Jones View Post
Older carbureted bikes and cars needed to be rejeted etc, newer ones with 02 sensors, computers etc does that automatically. Thatís why nothing has to be recalibrated with aftermarket exhaust.
GP, of all of the older bikes I seen on the dyno none needed rejetting after adding a header or can, they all ran very rich as delivered from the factory and the new header/can really didnít seem to affect the jetting at all.

At one of the seminars with the dyno-jet engineers there he said it was because almost all of the aftermarket exhaust doesnít increase the airflow through the engine so no jetting needed. Like Iíve said before a very few aftermarket exhaust will make about the same h-power & torque and Avery rare few might make 1-2hp more, most made less, some a lot less.

But the real gain was that almost all weighed significantly less than oe. Thatís where the real gains were.

Now changing the airbox to like individual pods or just modifying the airbox to increase airflow almost always required some rejetting.

Fuel injected bikes were a little easier because a lot of them had the ability to self adjust some as you stated but generally speaking they really mirrored the carbíd bikes jetting with most being fairly rich. Thereís a lot of reasons for running things so rich but ultimately it is to keep warranty cost down. At least thatís been my experience on it. And like I said the whole ďfactory super lean for emissionsĒ thing is just pure myth, just isnít true. My .02

Steve P
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Ride more,, worry less !
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