Rev Limter On Na R33?

[SKiT_R31]

The turbo does pose a huge exhaust restriction, but my point is that larger exhaust doesn’t mean less backpressure. If the turbo car isn’t making enough power and exhaust gas, the exhaust from the turbo back reacts just the same as it would on an N/A.

[zebra]

No but removing the standard cam shaft and putting the aftermarket cam shaft in did mean it had more valve overlap

Sooooo...

You put a bigger cam in and you lost some bottom end....funny that.

[tm_r33]

No the car had the cam in it the whole time I owned it. Changing the exhaust around months after I bought it was where it lost power at lower rpm.

[zebra]

Ahk gotya

sounds like it needed a fiddle with the tune then.

[bozodos]

wasn't there a big debate thread about backpressure on N/A cars a while back that concluded that for a street driven car (ie not one with all high end torque and power), that proved the point that there IS such a thing as too big?

I've seen evidence to support this ancedotally in real life as well.

Suffice to say, an N/A Skyline with a loud exhaust sounds much like a piped Holden V6.

[R31 POWER]

hop1308, can you PLEASE put a vid up of this thing on the brake on limiter!

[hop1308]

im gonna put in another cannon, 5 inch tip on the other side of the back. wont connect it to anything though. should add a bit of kw at the wheels.

[G0DZLR]

hahahaha. nice.

this is what a 3" straight pipe on a TURBO sounds like. no restriction, not too big, perfect size.

[mad082]

im gonna put in another cannon, 5 inch tip on the other side of the back. wont connect it to anything though. should add a bit of kw at the wheels.

ahahaha, good stuff, LOL

as for the debate above about back pressure, back pressure is bad on all modern motors. end of story.

the whole exhaust size debate unfortunately has nothing to do with back pressure on modern cars, that is just what people use as the excuse for why not to put a big exhaust on, however they are actually incorrect. you don't want to increase back pressure. this will not give you any sort of power gain anywhere in the rev range. the real reason why you don't want to go a big exhaust has to do with the scavenging effect in the exhaust. a given exhaust size will have an ideal amount of flow from a motor where the exhaust gases flow the most effeciently. it is a mix of finding the ideal gas velocity where the gases from one cylinder aren't slowing down to a point where the gases from the next cylinder to fire are then being slowed down by them, etc. the problem is that you can only really have an exhaust that is most effecient at 1 end of the rev range. car manufacturers make this at the lower end of the rev range where you spend most of the time driving. no point having an exhaust the flows really well at the top of the rev range if it means a drop in torque at the sort of revs you are at when driving on the highway so you have to drop down a gear evertyime you come to a hill. a race car on the other hand spends all of it's time at the top 20 or 30% of it's rev range so naturally it will need a bigger exhaust and any losses to the lower end of the rev range are of no great concern as it will never be at the lower rev range.

people seem to be too concerned with putting exhausts on road cars that will give them higher max power outputs on a dyno, as they think that this means they are gaining power everywhere. this isn't the case though. if you drive your car as a daily, very rarely rev it above 5000rpm and never take it to the track or drags, then even a 2.5" exhaust on a skyline is too big and you would find that the car would be nicer to drive, quicker (for the rev range you are driving in) and probably more economical with the stock exhaust.

[SKiT_R31]

^ That’s pretty much what I was trying to say.

Funny story though, the best sounding exhaust I've heard on an RB was a mandrel 2" ID straight through system (with resonator and perforated glass fibre packed muffler). Car had a deep rumble at idle, and an incredibly responsive real "barky" rev, sounded incredibly tough just cruising at low rpm and screamed under throttle. The car made 108kW at the wheels on the dyno, not long after he fitted a press bent 2.5" system, sounded ratshit (raspy and cackly) and a larger TB, back on the dyno, 108kW at the wheels.

He then turbo'd it, made 165kW at the wheels, put a mandrel 3" system on it and made 168kW at the wheels.

Same dyno, and obviously power figures do fluctuate with humidity and air temperature, even with correction on, my point is really to show there was no difference as none of the pipes were actually posing a restriction.

Comparing the before and after graphs, the line up perfectly. To drive the N/A the car from 2" to 2.5" was a rough change, its weird but it made the engine feel looser, but didn’t make it feel quicker, almost like it had less power (this would be from part throttle efficiency I’m guessing). The turbo 2.5" to 3" made no noticeable difference apart from a smoother and better note.

I guess my point is, for the mild (almost un-noticeable) changes in drivability, as long as the exhaust can flow the power you are really only doing it for the sound you like, if he likes his sound then fair enough. Usually the power difference people notice from changing exhausts is from the more efficient mufflers, as most people wouldn’t really be restricting their systems with stock pipe diameter (and probably wouldn't be matching their power in the pipe efficiency range from either the stock or larger pipes).

Edited November 15, 2010 by SKiT_R31

[hop1308]

hop1308, can you PLEASE put a vid up of this thing on the brake on limiter!

it doesn't have a limiter, sorta got discouraged from it here..

but as for the performance, ive compared it to a mates non turbo r33 with a stock exhaust, no cannon. and i feel the difference in performance with mine performing better, as early as the 4rpm mark. but for fuel economy, it drinks petrol like no tomorrow, it takes as much as or even more than a 3L car we have.

[SKITTLES]

hop, you've taken this criticism well.

I would have said "f**k you all" and never come back..

[mad082]

it doesn't have a limiter, sorta got discouraged from it here..

but as for the performance, ive compared it to a mates non turbo r33 with a stock exhaust, no cannon. and i feel the difference in performance with mine performing better, as early as the 4rpm mark. but for fuel economy, it drinks petrol like no tomorrow, it takes as much as or even more than a 3L car we have.

is that just by the seat of the pants, or side by side race? if it is just by the seat of the pants, then it may "feel" quicker, but you may find that in a side by side comparison it is slower. the reason being that with the stock exhaust it will pull pretty well lower in the rev range and then it will start to choke a bit up high. while with your exhaust it will be slower in the lower rev range and then the further up the rev range you get the better it is getting, so it gives the illusion that it is pulling harder, but it may actually not be pulling mucher harder, or even as hard as the stock systemed car. that is the problem with the seat of the pants dyno. it feels like your engine is coming to life higher in the rev range while his would feel like it's dying off, but that doesn't mean yours is faster.

i'm not saying it isn't faster, just saying that the seat of the pants dyno can lie.

the extra fuel usage is prime evidence that you are losing power. you are having to apply the accelerator more to go anywhere. if you were to put a smaller exhaust on then you would gain power and therefore effeciency, so you wouldn't have to apply the accelerator as much to go at the same speed.

[GTRPowa]

In the exhaust is a column of air, when pushed from one end, that end compresses the air slightly until the whole column of air is moving. This is your backpressure. You'll get this with a large exhaust as you have a larger column of air, with more weight. Moving this takes time, and it what causes the so called loss of power with large exhausts.

With an exhaust of a smaller diameter, the column of air is far smaller. This can be pushed with less resistance.

Now imagine this column of air moving again, and you then close the throttle, the airflow stops at the engine, but the column of air in the exhaust still has momentum. At it keeps trying to move it can create vacuum near the engine. While it's the most excessive way to explain it, this is your scavenging, it's the will of the column of air to move through the exhaust, and as it does it creates vacuum in the cylinders, taking all the exhaust out of the cylinder and even pulling a small about of intake charge in as the exhaust valves overlap.

----

And OP, get the limiter, it's a few hundred to make whatever noise it will make on your setup. Shit, some people have a few hundred spare and they waste it on pokies, if you don't care about the money go for it.

[KezR33]

this thread made me youtube na R33 sounds

youtube description

"7" cannon Varex muffler with 4.5" tip and 2.5" inlet on a non turbo R33 Skyline."

imo this sounds bad

lol I uploaded that. It's my old car.

Never judge the sound of an exhaust based on a youtube clip. Firstly I used a $80 digital camera with the world's worst microphone, secondly the Varex does an amazing job at muffling the noise of your exhaust. It literally went from a loud drone to whisper quiet, something you can't tell from that video as the camera is sitting 2feet away from the exhaust. No doubt the proximity also affected how the exhaust sounded, which IMO wasn't that bad.

[FullBoooost]

hahahaha. nice.

this is what a 3" straight pipe on a TURBO sounds like. no restriction, not too big, perfect size.

great sound!

[TwoCents]

this thread made me youtube na R33 sounds

youtube description

"7" cannon Varex muffler with 4.5" tip and 2.5" inlet on a non turbo R33 Skyline."

imo this sounds bad

Have pretty much the same setup on my car atm, it does sound much better then that video in real life.

My sound from inside the car...

[zebra]

http://www.circletrack.com/enginetech/ctrp...ning/index.html

Good read for those who think a cheap shit set of headers/extractors are just as good a a REAL set.

now no doubt there are limits to how much room you have in the engine bay etc.

[zebra]

Also note my earlier post about how power/torque characteristics are all in the primary pipes, not the exhaust pipe after that.

[mad082]

you also have to remember that that article is about race headers where you generally won't have much of an exhaust after the headers, so some of those principles have to altered slightly. that is why it also makes no mention of power gains/losses from the exhaust system at all, but you will still get power gains and losses from catback systems