How to make Greddy SP fit 92 4WS ? - Honda Prelude Forum

yohan420 · 01-05-2004, 09:31 AM

I will be upgradeing to a vtec in the future ... SO, I dont want to modify my cat-back greddy SP ..

I did some searching and only found that I should modify the flange attaching to the CAT because the holes are in a different place ...

Because I plan on going vtec in the future, and also heard that the Vtec cat-back is shorter than vtec...

Should I get a longer cat and modify the flange from the down/flex pipe?

What would be the best way to modify this to fit my application?

cleanLude · 01-05-2004, 10:01 AM

So you will be using an aftermarket cat then?? I beleive that you can get an aftermarket cat that is a bit shorter and they will have to add piping to it to fit ur current situation....you should add the piping on the side towards the flexpipe ,that way you can shorten that added pipe later on along with changing the flange(if necessary)...no need to modify the flex pipe of your greddy...However, i dont think that the VTEC exhaust is shorter than the non-VTEC...only difference is the flanges...

yohan420 · 01-05-2004, 12:31 PM

I plan on using everything stock that I have providing it will fit .. but I dont want to modify the SP flanges at all ..

somebody on honda-tech said that the vtec exhausts are too short for the SI ..and I think to modify an H23 header to fit H23 you have to add length onto it ?? ..

Really wish I knew the difference ... ill do s'more searchin this aft at least for the vtech/si cat's and see if they list length anywhere ...

cleanLude · 01-05-2004, 02:14 PM

That Honda-tech guy is wrong...i have a 94 H23, and since u kno that Greddy has no love for us H23 peeps, i picked up a Greddy SP exhaust for the VTEC as well...since you dont wanna modify the greddy flange, you can modify the cat flange that its supposed to bolt up to...oh yea, btw, modifying the greddy flange will still allow you to bolt it up to a VTEC model if you want to...all the muffler shop is going to do is widen the bolt holes by cutting out the outsides of the flange, so any flange that is smaller will still fit without any problems, as long as you still have the gasket...hope this makes sense...

willmbrk · 01-05-2004, 02:35 PM

Vtec exhausts are just a little longer than the SI exhaust. You just have to cut a little off the CAT flange, and it should bolt up fine. At least mine was that way.

yohan420 · 01-05-2004, 03:22 PM

What's the diff of Vtec / Si stock exhaust theN?

I know the headers need modification as well .. I'm not sure if this is off of the head or the downpipe though .. and the cat is different as well .. hmm...

willmbrk · 01-05-2004, 03:31 PM

According to RS*R, the only difference is length. I called them asking about the difference.

yohan420 · 01-05-2004, 04:38 PM

but length on what part is the real question ...

An H23 Header can be modified to fit H22 engine but I'm not sure how, as stated above..

1. The vtec CAT is longer by ~1.5"
2. SI Cat has a different flange

Theres 3 sections to the cat-back exhaust .. Muffler, piece with resonator, and the other piping..

Also, there's the downpipe/flex pipe .. really wish I could see an Si and Vtec on a lift and measure every peice so I could add length where necessary ..

MidNKight-lude · 01-05-2004, 06:41 PM

i never knew there was a different in cat. but teh exhaust length is the same!?!?!. just modifiy the greddy exhaust. just bore/hone the holes out a little more inward, and ti will fit. no cut or welding involve, then you can reuse it on your vtec swap.