How much power can the Mugen header and cat-back exhaust make?

I finally got a chance to dig up my bone stock dyno files from March and compare them to the runs I did last Wednesday afternoon. I was really impressed with the results. The 2 runs were done on the same dyno at ERT in Delaware, and the atmospheric conditions were identical on both days.

2000 Honda Prelude Base 5spd
Run 002 - Mar 21, 2001
Milage:~15,000
Conditions:49.65F, 30.17in.Hg., 0ft.elev, CF=0.95
Mods:None, Mobil1 oil

Run 003 - Nov 21, 2001
Milage:~27,000
Conditions:50.21F, 30.22in.Hg., 0ft.elev, CF=0.95
Mods:Mugen Header, Mugen CatBack, K&N drop-in filter in stock airbox, Removed air intake resonator, Mobil1 oil

My peak WHP went up 10.6HP, and peak torque at the wheels went up a modest 3.8lb.ft. These peak numbers sound like a nice gain, but they only begin to tell the whole story... The best part is the consistant and substantial gains across basically the entire powerband from 3500rpm onward. Gains of 4-8HP and 2-7lb.ft were seen from 3500rpm-4900rpm. And gains of 8-12HP and 8-12lb.ft were found at 6000rpm and up!

The one area that I found odd was that there was no significant change in power in the VTEC crossover range of 4900-5200rpm... Could this be a fuel starvation problem?

I recently saw another dyno of someone's OBD2 Prelude where the owner dynoed the "ECU reset". He dynoed before the reset and then after the reset and gained 3-5hp across the whole rpm range. I decided to try the same thing. But I got jack as far as gains go. I gained maybe 1hp if I was lucky. It was not a significant change on my car. This may have something to do with the relatively cool temperature conditions I dynoed under. It may also be something to do with my 2000 "OBD2ver2" ECU. I'm open to other theory suggetions...

Anyway, here are the plots...
SAE Corrected HP and torque:


Actual HP and torque:


I was happy with the results. 11+ warranty-legal bolt-on wheel HP is good in my book!

Andrew

 

Very nice... ~11~ whp is ALWAYS good.

 

how come the dyno chart is so jagged edged

 

That's because I turned the "smoothing" option to the lowest setting in the Dynojet viewer to get that extra 0.3 peak horsepower... It was a difference of like +/- 0.5HP between the highest and lowest smoothing setting...

Andrew

 

Where exactly did you get your dynoing done. I live in NYC so you are not that far out. Do you have any numbers for contact and costs?? Thanks in advanced I need to know how well my car is running with the current setup.

 

I had the dynos done at European Racing Technologies (ERT) in Willmington, DE. Their web site is http://www.europeanracing.com. They have contact info and dyno pricing on their web site. You can get a half hour of dyno time for $75 on a weekday, and I think an hour is like $130. You can also rent the dyno for half days or full days for a greater discount...

ERT is owned by DuPont Motorsports. DuPont campaigns an extremely competive BMW team in the Speedvision Touring Car series. They actually tune their race cars on this dyno. So I assume that it is very acurate. In fact, when I was there last Wednesday, that's exactly what they were doing. They were setting up to tune the race cars as soon as I left...

Andrew

 

If you would please...

How large is the collector on that header? in inches? and what size is the exhuast?

its it all 2.5"?

Jeff

 

The Header collector is 2.25". The cat back piping is also 2.25" all the way through. The bottleneck now is the stock cat which is only 2.0" AFAIK. Do you think I'd see any subtantial gains by getting a 2.25" Carsound cat custom made?

Also, any ideas why there were no gains at VTEC crossover? I'm thinking a V-AFC and tuning would help, but I'd rather not do anything that would void my extended warranty...

Andrew

 

Probably when setting your Vtec to engage like 300 rpms earlier you will get
better results with your current setup. But until you get the VAFC or standalone you wont be able to find out.

 

are you sure it is 2.25 all the way ?

cause the Mugen B18 exhaust is 2.4 to 2.6" all the way ..

i don't see why the echaust for h22a would be smaller

i don't think u will gain a lot by replacing the cat with 2.25
make it 2.5 being there
cause there are lots of stuff inside the cat itself that makes interferenceses so ..

 

Yes. It is 2.25" in diameter. I measured the header collector and the b-pipe from the cat-back at the flanges that mate to the cat. The piping diameter does not appear to change in diameter elsewhere...

Andrew

 

mmm

sorry if you answered previously..

the piping from the cat to the muffler..
is it 2.25" OD or 2.5" OD and u estimated 2.25"ID ?

this is rather important..as i will be doing custom exhaust on my car..i would like to folow some prooven designs
exactly like the mugen ( YOU LUCKY BAST!!! aahha

and how do you like the sound?


thanks for the info..
( i seriosuly thought that the mugen exhaust for the lude had a 2.5"ID-OD diameter up to te exit..

could you too check the muffler size quickly ?

 

The innner diameter of the piping at the flanges from the Mugen parts that meet at the cat are 2.25". The diamter of the flanges on my stock cat are only 2.0" I think.

I'm not sure what you mean by the muffler size... But the exhaust tip diameter is 3" - if that's what you were asking... (3" is a bit big for my tastes, but oh well...).

The sound is glorious. I love it. But don't let people tell you that it is quiet though. It is considerably louder than stock - especially when it's running hot. It's a nice deep mellow tone though.

Andrew

 

cool!!

nah what i meant is the size of the piping in between the cat and the muffler..that u answered.. so it's only 2.25" ..eeh ok

and the size of the piping that goes in and out of the muffler..not the tip
ahha

you see i am making myself a custom exhaust..with a Mozart muffler i got from ebay cheap cheap
it is an exact replica of the mugen twin loop..only it is for the integra..
and a bit bigger..it uses 2.5" piping though..
adn the only mandrel bent shop i found near here does 2.5" piping and up!
so as for now i can't get 2.25"
but since my muffler is 2.5 i might go with 2.5"OD if they can work with it..
i hope i won't get a too awfull sound

and i can't change the cat as it is not allowed in the class i am racing in..

 

It sounds like your 2.25" measurement is the ID?? Therefore it's probably 60mm OD tubing. Tubing is measured by it's OD and the ID is determined by the wall thickness or gage. US spec 16g measures .065" and 18g is .049". The Integra Mugen ccat back is also 60mm OD (2.36") but actually gets smaller in the twin loop muffler, somewhere around 2-1/8" to 2-1/4".

Yes a 2-1/4" Carsound cat will make a difference over your stock cat. The stock ITR 2" cat flows around 224cfm at 28inches of vacuum while the 2-1/4" Carsound flows 343cfm. If your interested I build custom lengths cat also, so they're will be a direct bolt in for your application.

 

It IS actually 60mm ID. After I posted this on another board, someone corrected me. It is actually 60mm ID (2.362") at the collector. When I said it was 2.25", this was based on me measuring the piping with a wooden gradeschool ruler... which is not the most accuate...

Yes, I would be interested in a Carsound cat - but only if it is a direct bolt-on for stock with the secondary O2 sensor bung and all...

I was very encouraged by the gains I saw with basically just the header and cat-back on my car. And I have yet to see a dyno of an aftermarket cat on an H22a, but I have to believe that there are some gains to be had there just based on the size of the stock cat...

Andrew

 

It sounds that your header my be comparable to the ITR JDM collector. I think the Mugen cat back is 60mm OD, correct?

Can you send me a picture of the cat installed? If you give me the overall length I can build it to that.

 

SMSP: Here's a picture of my cat converter from when I did the exhuast install. Mugen Cat back, Stock Cat-converter, Mugen header. The cat itself is everthing under the cat heatshield there. The secondary O2 bung is at the rear of the cat (on the left in the pic). I guess this is the same with most OBD2 cars...



I will not be able to measure under my car anytime soon... This sounds like a project that may need to wait for spring...

I do have some more detailed pics of the header/exhaust install somewhere. I'll forward them to you when I find them.

Andrew

 

I was wondering if anyone knew where most of the gain is coming from, the Mugen header, exhaust, or the synergy between the two ? The reason I'm asking this is I wonder if similar results could be achieved with say, a DC header.

Also, anybody have this setup with a CAI? What kind of gains have you achieved with that?

Thanks!