Jimmythebiz

iTrader: (1)

Hi Guys,

Right I have a 3inch sports cat downpipe..(My car is a 1998 STi Type R)..

It used to then go to a Blitz Nur Spec R exhaust system-this was too loud so is now sat in my garage.

I then took part in the Haywood and Scott group buy and bought a 3inch system with the Jap backbox- this was too loud so sent the centre section back and got them to weld a silencer in the centre pipe this was still too loud for my liking.

I have just come back from the ring and i didnt want to arrive with a head ache so i put the standard exhaust system on it with both the cats.

If i fit a japspeed de-cat thats 3inch bell mouthed to a 2.5 inch flange and run with the standard exhaust thereafter how many bhp will i be losing over my full de-cat 3 inch system?

What power levels do you need to swap from a 2.5 inch system to a 3 inch system?

Sorry for waffling on...

Cheers
Jimmy

banny sti

iTrader: (68)

I would imagine 2.5" would become a restriction at around 400bhp below that there would not be any real difference.

Banny

TingTongPJ

iTrader: (24)

i had this sort of issue with my car,

spent loads on a new engine mods and ecu etc and was supposed to easily break 400bhp.

mapping went ok but only got 1.5 bar of boost then when on the rollers for a tweek and check the power only 372bhp.

was so dissapointed.

someone then noticed i only had a 3" bell mouth down pipe 2.5" centre setion then back to 3" at the rear on my exhaust, changed it to a 3" full system remapped and then 1.8 bar of boost and easily over 400bhp.

i was told that 372bhp on my previous exhaust was excellent and normally you can only run them up to 350bhp ish.

Jimmythebiz

iTrader: (1)

This is all interesting to know..

I am only just running over 300ish bhp, so it looks like at the moment 2.5 inch would be fine...but am i alright to use the standard sti centre section and back box?

I have a 3inch exhaust system as mentioned before but its too loud and i like track sessions, does anyone do a highpower 3 inch system with a jap style back box but with a nice quiet 98db output?

Would then sell my h&s scott system and blitz system then would have enough room to put the car in the garage again.

Cheers
Jimmy

scoobyc

iTrader: (2)

My bro had the HKS silent system on his evo. He produced 89 db iirc at bedford. Sounded nice, brilliant build quality but it was on an evo. yuk

I have the H&S scoobysport back box. Its not jap but its also not too loud. My crappy hand held meter rekons 112 db, but ive been on a couple of track days n not been pulled yet. I rekon its prolly more like 102db.

Put a silencer in the middle and im sure it will be well within the limits of 100db.

Doesnt look the best tho!

Jimmythebiz

iTrader: (1)

lol...i had a silencer added to my H&S system and it didnt really do much...

Just looking at the HKS website...

"Constructed of fully polished SUS304 Stainless Steel, the HKS Silent Hi-Power exhaust system was designed for enthusiasts seeking the highest quality performance exhaust system with only a slight increase in exhaust noise."

Sounds good to me, anyone running one of these? What bore are the pipes?

Cheers for all your responses
Jimmy

scoobyc

iTrader: (2)

I meant i have the 3" scoobysport fully decatted with just the backbox. which comes in under the radar for the track days ive done. Add a silencer into my system and im sure it will be fine.

I was really impressed with the quality of the HKS, it fitted perfectly too.

Hope someone can commend on what they are like on a subaru. Might be some videos on youtube of it?

Jimmythebiz

iTrader: (1)

Hey Scoobyc am i right in thinking the scoobysport system is the same as the H&S system?
So it could just be the jap style HKS backbox giving out the DBs if i swaped the backbox for the smaller scoobysport backbox i could be on to a winner?

Do like the idea of the HKS system, might have a look on youtube later as i am at work at the moment and dont have access.

Cheers again!
Jimmy