Took some cats off, then put some on..........
Discussion
As the title says, I removed the last 4 close coupled cats in my V12 exhaust manifolds, and then put some high flow cats back on, in place of my secondary decat pipes.
Not being too concerned about the chances of cat ingestion, I based this latest exhaust mod on the need for the final EASY modification for improving the gas flow through the engine. Following on from my previous posts on my intake mods, I never bothered with posting about the hugely common secondary decat modification. Further improvements will require cylinder head porting and camshafts etc which I will not undertake unless there is any reason to require head removal. The airbox mod or the GT4 airbox delete are only worth around 2 bhp so I will let the car continue to snort clean, dry air through the OEM cold air intake snorkel.
So, to release some more performance, I went for these 6 branch tubular manifolds
in combination with these high flow cats...
The tubular manifolds were specialist manufactured using the original cylinder head flanges and downpipes from an original set of V12 manifolds.
The new manifolds did not come ceramic coated so I used some specialist thermal exhaust insulation
https://www.designengineering.com/black-glass-fibe...
(No affiliation etc, etc, etc.)
that is very widely used in motorsport, and virtually essential on high performance turbocharged cars, to reduce underbonnet temperatures and protect nearby components.
The time to do this is most certainly when the manifolds are off, on the bench and easily accessable.
With the manifolds back on the car, all the nearby components are protected.
All that was then needed was to remove the secondary decat pipes and install the new high flow cats in their place. The O2 (Lambda) sensors were quite difficult to remove and 2 were impossible, so unfortunately, 2 needed replacing. With using the original manifolds as a basis, I also had the advantage of being able to refit all of the original heat shields. The wiring looms were extended to reach the new sensor location.
Finally, the ECU was remapped to take into account the new O2 sensor locations and to make the most of the improved flow.
I am now looking forward to re-running the car on the dyno to measure any improvements.
No seat-of-the-pants dyno result yet because road conditions have been very bad but aurally, it is slightly louder but with a real dirty crackle, it certainly sounds like it means business.
Not being too concerned about the chances of cat ingestion, I based this latest exhaust mod on the need for the final EASY modification for improving the gas flow through the engine. Following on from my previous posts on my intake mods, I never bothered with posting about the hugely common secondary decat modification. Further improvements will require cylinder head porting and camshafts etc which I will not undertake unless there is any reason to require head removal. The airbox mod or the GT4 airbox delete are only worth around 2 bhp so I will let the car continue to snort clean, dry air through the OEM cold air intake snorkel.
So, to release some more performance, I went for these 6 branch tubular manifolds
in combination with these high flow cats...
The tubular manifolds were specialist manufactured using the original cylinder head flanges and downpipes from an original set of V12 manifolds.
The new manifolds did not come ceramic coated so I used some specialist thermal exhaust insulation
https://www.designengineering.com/black-glass-fibe...
(No affiliation etc, etc, etc.)
that is very widely used in motorsport, and virtually essential on high performance turbocharged cars, to reduce underbonnet temperatures and protect nearby components.
The time to do this is most certainly when the manifolds are off, on the bench and easily accessable.
With the manifolds back on the car, all the nearby components are protected.
All that was then needed was to remove the secondary decat pipes and install the new high flow cats in their place. The O2 (Lambda) sensors were quite difficult to remove and 2 were impossible, so unfortunately, 2 needed replacing. With using the original manifolds as a basis, I also had the advantage of being able to refit all of the original heat shields. The wiring looms were extended to reach the new sensor location.
Finally, the ECU was remapped to take into account the new O2 sensor locations and to make the most of the improved flow.
I am now looking forward to re-running the car on the dyno to measure any improvements.
No seat-of-the-pants dyno result yet because road conditions have been very bad but aurally, it is slightly louder but with a real dirty crackle, it certainly sounds like it means business.
Craig elam1 said:
Good work that man!!, any chance of a guide to removing the manifolds please
Im keen to remove primary cats to negate the possibility of ingestion, also lowers engine bay temp considerably plus some free bhp.
Excellent winter project
Yeah guide to remove the manifolds would be great, I've heard you need to cut them in half to remove them, and a flange is welded on for reassembly.Im keen to remove primary cats to negate the possibility of ingestion, also lowers engine bay temp considerably plus some free bhp.
Excellent winter project
Evnin all, looks like gerrys busy, i know from experience in the trade pre christmas can go mad!,
Anyways having a google search "db9 manifold cat delete" clicked images , scrolled down a bit and theres a picture of a v12 manifold thats been cut to facilitate removal with subframe in place,( i didnt want to nick the picture for copyright etc), another piece of the diy de cat puzzle ?
Anyways having a google search "db9 manifold cat delete" clicked images , scrolled down a bit and theres a picture of a v12 manifold thats been cut to facilitate removal with subframe in place,( i didnt want to nick the picture for copyright etc), another piece of the diy de cat puzzle ?
crispyj said:
Nice work 8tech,
Where did you get the exhausts done?
Sorry all, trying to get the next 3 weeks worth of work done in the next week to get Xmas off.Where did you get the exhausts done?
The manifolds were done at David Appleby Engineering and they supplied the new cats too. Dying to get it back on the dyno but thats luxury playtime I simply do not have at the moment. Exhaust wrap is a thing I used all the time when everything I had was turbocharged but it is almost as effective on NA engines too. Main use here was to protect that cramped engine bay with plastic arch liners instead of metal inner wings!
Cheers,
Gerry.
Sorry I hate doing this.....
but next time before you start wrapping the manifold dampen the wrap so it stretches a little as you put it on so you can get it nice and smooth and it will tighten when it drys.
Then once it’s dry please please please once dry use the silicon spray over the top so it sets hard like a broken arm plaster.
What you’ve done there is equivalent to using plaster of Paris for a broken bone but not used any water.
No offence intended.
but next time before you start wrapping the manifold dampen the wrap so it stretches a little as you put it on so you can get it nice and smooth and it will tighten when it drys.
Then once it’s dry please please please once dry use the silicon spray over the top so it sets hard like a broken arm plaster.
What you’ve done there is equivalent to using plaster of Paris for a broken bone but not used any water.
No offence intended.
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