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Throttle Response - Dump Pipes & Hi Flo Cats

NISGTS

By NISGTS,
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NISGTS Rookie

NISGTS

Posted
Posted

Hi Guys -

May be someone out there has a conclusive answer, to the question as to whether throttle response and mid range torque is scarificed for top end when installing a 3" dump/front pipe and hig flo cat.

I've heard some conflicting reports but basically 2 exhaust guys have now said that I will increase turbo lag and scarifice throttle response by opting for a 3" dump/front pipe and hi flo cat. They have said that that the 3" dump/front pipe and hi Flo cat will really only give better top end improvement but I'm not interested in this as I want the car to have good throttle response and less turbo lag. If what they say is true then it may be bettter for me to spend the money on an APEXI FC ECU which would give a better all round result

FYI - I have a R33 GTST series II with a NISMO 3.5 " cat back s/s exhaust, the car is currently running a turbosmart boost controller (ie on about 9psi), K&N Panel Filter, ligthened flywheel, GFB Stealth BOV and a NISMO hevay duty clutch . The car runs fanstically and is very street drivable. The guy who previously owned the car in japan worked for NISMO and I'm thinking that for the reason increased turbo lag that this may explain whay he did not run a Full Exhaust on the car.

I would appreciate any INPUT from those who have undertaken the dump/front pipe and hi flo cat to their R33 GTST

Thanks

NISGTS

REdgtst Proficient

REdgtst

Posted
Posted

I would have thought a high flow cat woudl increase responsiveness? Not sure about turbo lag however? More flow = less restrictive = more response (im most general situations anyway). I have a cat back system aswell and am looking at getting a split 3" dump/front pipe and no cat (from what i have heard i can expect approx 20kw minimum power gain and more response). Bosimporting have dyno proof on one of these forums of the advantage of the split 3" pipe and high flow cat versus stock parts and they got quite a big gain in HP.

NISGTS Rookie

NISGTS

Posted
  • Author
Posted
I would have thought a high flow cat woudl increase responsiveness? Not sure about turbo lag however? More flow = less restrictive = more response (im most general situations anyway). I have a cat back system aswell and am looking at getting a split 3" dump/front pipe and no cat (from what i have heard i can expect approx 20kw minimum power gain and more response). Bosimporting have dyno proof on one of these forums of the advantage of the split 3" pipe and high flow cat versus stock parts and they got quite a big gain in HP.

Thanks for the response.

I'm led to undertand that the increase in k/w is at the top end, and that the freer and less restrictive the flow the less back pressure, this in turn neccessitates less response and and bigger turbo lag.

I would appreciate feed back from any one who has undertaken the dump/front pipe with a hi flo cat, to see if their has been better throttle response and less turbo lag.

The issue with some of the dyno figures that are given and the gains attributted to the dump and hi flo cat is that it focuses on top end and the k/w gain going flat out, at hi to maximum rpm. A good street car is one that can give the best overall response, and linear torque through out the rev range, not just a large burst.

bilbo117 Rising Star

bilbo117

Posted
Posted

hmm.... when i got my frontpipe and dumppipe i noticed an increase in responce.... i was under the impression that with any turbo car the bigger the exhaust the better? as u want the highest pressure difference possible on your exhaust wheel of your turbo??

The Dan Grand Master

The Dan

Posted
Posted

The exhaust system does not give your engine it's backpressure.

The turbo does. By changing the exhaust system you allow the turbo to extract gasses more freely which means that turbo response INCREASES. Boost will come on sharper and you will be less likely to spike or overboost.

The smaller the exhaust system, the less boost you are able to run.

I know the above to be fact, however, I will say this:

I don't personally have dyno proof of when the power change is in a 3 inch system but I can assure you that it definately won't make it laggier. It will only remain the same or increase response.

r33freely Enthusiast

r33freely

Posted
Posted (edited)

yes, bigger exhaust less restriction and more response down low as well as up top

there is a good thread on here somewear where sydneykid was dyno testing different cats and from memory the best was a four inch high flow cat, even on a three inch systyme

and i personly must recomend the twin dump pipe from ces racing.com.... theres defenently 20+ kw there!!

i could not belive the difference it made as far as low rpm spool is concerned and it keeps the power on at high rpm and after the gearchange!

Dave

Edited by r33freely
TommO Grand Master

TommO

Posted
Posted

I noticed a HUGE difference after fitting a split dump pipe and hiflow cat. Car came on boost a low earlier, was much nicer to drive down low and off boost, and top end was significantly improved too. Easily the best mod you can do, and you won't look back!

I got the split dump pipe from CES Racing as well ;)

TokyoTaxi Veteran

TokyoTaxi

Posted
Posted

Maybe you guys would know...... I've got a complete 3" exhaust stsyem but the cat is a reasonably old ( maybe 4 years ?? ) 3" catco. Anyone got any idea how much difference it would make to fit a new metal cat / stainless steel cat etc ?

Will a top $ cat make any real difference to the performance you've talked about ?

r33freely Enthusiast

r33freely

Posted
Posted

my guess would be that your 4yr old cat would be full of carbon and crap, your proberly best to go the 4"... ill try to find that thread i was talking bout before

i know you can get a good high flow 3" stainless steel cat from just jap in sydney for about $170.00 if thats any help

Dave

Cubes Grand Master

Cubes

Posted
Posted

I went from a stock exhaust to a full 3", turbo back, highflow cat, resonator, large rear muffler. All straight through.

The full exhaust made made the car feel as if it was freeier at low rpm, every where had picked up power/response.

TokyoTaxi Veteran

TokyoTaxi

Posted
Posted
my guess would be that  your 4yr old cat would be full of carbon and crap,  your proberly best to go the 4"... ill try to find that thread i was talking bout before

i know you can get a good high flow 3" stainless steel cat from just jap in sydney for about $170.00 if thats any help

Dave

I guess after 4 years it would be pretty crappy huh.....

Are the ones from Just Jap the ones with the stainless body & stainless biscuit ? ( with 200 holes per inch ) ?? I think they now sell those barrel style ones.

I'm just not sure how much difference a $450 cat makes compared to a $150 cat <_< ( Which, I guess, is the same sort of question as the first post ).

r33freely Enthusiast

r33freely

Posted
Posted (edited)

mine cost $650 from memory and that is the ceramic coated one wich was $100 dearer or so... looks awsome!!

ill send you a good close pic if you like, i also have pic of it next to the standard pipes ect

Dave

Edited by r33freely
Bobjones Mentor

Bobjones

Posted
Posted (edited)

Send pictures, I have been trying the get close up picture of the CES Split for ages,especially around the turbo/wastegate split and the re-entry of the wastegate pipe...

I had a thread up a while ago with a comparison...can't seem to find it...

EDIT: Found it :lol:

http://www.skylinesaustralia.com/forums/in...opic=86654&st=0

Edited by Bobjones
RANDY Veteran

RANDY

Posted
Posted

Damo.. should be! BATMBL sells his dump/down pipe for $400 in mild steel, and reckens it should yield 15kw.

The bigger dump pipes will flow more exhaust gasses, and gas when hot is a larger volume than when it is cold... so bigger piping up the front is going to account for a lot.

Apparently having a split dump pipe is better for flow, but only noticeable if the wastegate pipe is very long... like the combined dump/down pipe that BATMBL sells. The shorter "HKS" ones may not be any better than a single bellmouth design, as the gasses don't split from the exhaust for very long, and when it rejoins the exhaust the shortness of the dump means the wastegate pipe joint/weld comes in quite sharply.

Thanks for the replies guys... I think i'll give BATMBL's dump/down pipe a go seeing as it is a fair bit cheaper.

kimbod Collaborator

kimbod

Posted
Posted

The bigger the better. You are trying to get the gases away from the turbine outlet as quick as possible.If the dump pipe has seperation of the exhaust and waste gate streams , even better. Look at how much you want to spend and how you use your car and take it from there.

benl1981 Grand Master

benl1981

Posted
Posted (edited)

A 4 yr old cat shouldnt bee too bad. If it was a high flow 3" provided and you haven't got huge mods I wouldn't think this would be much of a restriction. If you're worried take it off and see if you can see through it. You can kind of tell if it looks restrictive...you won't be able to see through the other side. Actually the term high flow is a bit of a rort. I't more about the body size. A 3" high flow is usually just a slightly bigger body and flanges.

Edited by benl1981

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