Best exhaust for 89 CRX SI

Richy Gonzalez

Richy Gonzalez

New member
Guys,
I'm about to build my exhaust and wanted to figure out what is the best exhaust setup for my ITA 89 CRX SI. What I've seen so far are straight exhausts pointed down right before the rear tires. While that seems very simple and somewhat cheap, I would like to hear what people have had experience with.

pipe diameter (2, 2.25, 2.5) ?
lenght (4, 5, 6 feet)?
what type of muffler/resonator?

Thanks
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Richy Gonzalez
ITA 89 CRX - 2002 Season
 
Richy,
From Sport Compact car testing, the best header is the 4-2-1 DC sports header. Now, the unit is made to mate to a stock exhaust and is necked down at the end. Cut that necking off and the flange. This leaves you a pipe of about 2.5 inches. Go to the local exhaust shop and purchase a flex joint section of piping (the braided looking pipe stuff with solid ends on it) in 2.5 inches. Weld this to the header outlet. Now your exhaust will be able to flex relative to the header. Now, purchase a 2.5" Dynomax straight through cherry bomb shorty. These are about 18-24" in length. Weld this to the other side of the flex section. It will fit in the spot that the old resonator sat in the stock exhaust. Finally, get a 4' section of exhaust piping, again 2.5", weld it to the cherry bomb and use the old hanger that is just past the shifter on the bottom side of the car. Put a 45 degree turndown on, and you are done. I am around 90+ decibles, well under the limit. I tried it without the cherry bomb, just a straight pipe and was at the edge of 104+ decibels. Too high for most tracks.


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Brent Breon
Cendiv ITA #26
www.360racing.com
 
Brent,
I really appreciate the info. I will be running a 4-2-1 DC sports header. Also, I wasn't thinking about a flex joint. Thanks! I'll be sure to have them put one in. However, I'm a little surprised as to the 2.5 diameter. Did the car seem to loose any torque? I was guessing more like 2 or 2.25

...I can see it coming now, Honda = torque
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Richy Gonzalez
ITA 89 CRX - 2002 Season

[This message has been edited by Richy Gonzalez (edited October 22, 2001).]
 
Richy, I agree with Brent on the setup, that is the same way I did mine but I have 2 headers that I have playing with: A DC header and a OPM header and I prefer the OPM since it gave us more torque on the Dyno, the DC showed more HP but I would rather have torque.
Either way both are great headers.
Louis Boustani
ITA CRX 2
 
Louis,

Thanks that was the next question I was going to ask, what about the OPM header? I am curious has anyone tried looking at headers with the new rules for next year, i.e., modified chips. Any thoughts?

Dick Plank soon to have 91CRX as well as 81 RX7
 
I am very surprised that the OPM gives more torque. I was under the impression that the 4-2-1 gave you more low end torque and the 4-1 gave you more top end power. I went with the DC Sports for the low end. Now, when you through in what Louis has said and the possibility to run that rev limit up and dial in more fuel and ignition advance, you might be able to make a sizable HP increase at the top end with a 4-1 header. But, you still need that low end torque to get you out of the corners. One thing is certain, the first person to really figure out the ECU deal should have a sizable lead. Question is, will it help the VW, Honda, Nissan, or Saturn the most?


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Brent Breon
Cendiv ITA #26
www.360racing.com
 
Brent,

I think you hit the nail on the head. My ITA experience is all with rotary's but I suspect with the Honda you need to work on top end horsepower as being able to modify the chip should not only allow you to go past the rev limit, but you should be able to move fuel and timing maps to give you more top end.

My brother, who is a 25 year honda mechanic, is building the engine and his experience tells him 8000 RPM is not a big deal assuming you have decent rod bolts and balance everything. I don't think I can legally oversize those rod bolts, but I can balance everything very closely. I have talked to several people on the chips and have looked at both Edyne and Hondata. As it stands now I will probably have a guy in Calif do the box for me this year and next year play with it myself. Given this is a new car we will take most of the season sorting it out anyway.

Dick
 
Dick,
I think you will be surprised when you go to balance the engine. Honda does a great job out of the factory and it should be pretty darn close if you are reusing most of the parts and the stock flywheel. As far as the computer goes, I don't want to be the first one to spend the $1500 for the computer and injectors only to find out not much more power can be had without enlarging the Throttle body and fuel rails, but, that is racing. You gotta pay to play.

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Brent Breon
Cendiv ITA #26
www.360racing.com
 
Brent,

My epxeriences with the Mazda are pretty much the same, the shaft and counterweight/flywheel is near perfect out of the factory. And yes I am using the stock flywheel, etc, but question?

Non stock injectors? Maybe I better get the fastrack or read the rules again. I was not under the impression I could upgrade the injectors. If so it's a whole new ball game and talk about power. I don't have the SCCA book, but am looking at the Midwestern Council book, which 99% of the time follows SCCA rules and I can't find anything in it about injectors or throttle bodies for that matter. Lots of stuff out there to do that, right off the shelf, but I am of the opinion thats illegal. What is your take?

Dick
 
Thanks everyone for the info. Got the exhaust made with a flex piece and ordered a Dynomax round muffler.

Also, I know the post went a little off topic, but I'm also interested to see if anyone gets some real numbers with ecu+header+exhaust tunning
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Richy Gonzalez
ITA 89 CRX - 2002 Season
 
just a note on the ECU I just emailed Tom Fowler with some questions about various parts and Tom expects to have a programmable ECU available early next year. Sounds like the way to go especially if you have access to a dyno. If not I guess you have to depend on someone else who has the dyno and has tested it. Both Zdyne and Hondata have programmable units. I have spent some time talking to Zdyne and they have a live real time programmable ECU upgrade for the CRX. It is about $950 and they just load the standard upgraded file in it, but you can, on the dyno, make real time adjustments. Look at their web site Zdyne.com and check it out. One of the guys did post on this site his knowledge of both Zdyne and Hondata some time back. Hondata also sells a gasket for the intake system which cools the air coming in, their website has the details on that.

What I realy don't know is how much extra we are going to get for all of this. I guess we will figure it out in time. I think I will wait until I see what Tom has.

Dick Plank
 
I believe the 2" collector of the DC is a little restrictive on the top end for the D16A6 engine. I build my ITA header with a 2-1/4" collector and recommend running all 2-1/4" tubing for the exhaust. When picking a resonator/muffler just make sure that the flow path is smooth.
 
Perhaps because I hate dealing with the Comp Board, I am amiss on this new rule change. What is the rule change for next year?
 
Sorry, I'm a little late on this topic. Whats the rational of getting a flex tube instead of just using the donut flange thats normally used?
 
I prefer to use the donut/ball/socket joint since the bellows in the flex tube isn't as smooth. You can actually get bellows pieces with sliding inner tubes of sst but these are very hard to find, very expensive and don't offer as much movement.
 
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