Why Is My Skyline So Slow

[adis]

does unbolting exhaust before cat help turbo cars or do the opposite?

Edited February 25, 2010 by adis

[mad082]

on your power setup it wouldn't make a huge amount of difference. but should make it a touch quicker

[SKiT_R31]

lol adis, either there is something wrong with your car, with your driving, or you didnt have anywhere near that power on the day. I've seen multiple R33's with stock ECU's + mods break into the high 13's. The R33 coupe in my driveway has 245 falk's on 18's and it really struggles with traction when hitting boost in first and/or quick shifting second, and yes it chirps third, and power wouldn't be near yours, maybe 170ish..........

This is my drag run in my dirty R31 wagon, with stock VL turbo management, and 10psi on a KKR430, FMIC, 2.5" sidepipe (no mufflers). Ran consistant flat 14's, the worst being 14.18 and the best being 14.02 (spewing that i didn't crack 13's) the car would be lucky to have 160kW at the wheels, and is of similar weight to your R33. (32C track temp)

[Tony de Wonderful]

The temperature of the gasses inside the exhaust are important. The more heat you can trap in the exhaust the better. The hotter the gases, the faster they travel. Since thermodynamics is a study of energy conversion between heat and mechanical work it is relevant. Why do you think keeping as much heat inside of an exhaust manifold and exhaust housing is an important part of spooling a turbo. The hotter you can make it, the better. So while i agree on this discussion on NA cars it is mainly fluid dynamics, thermodynamics are just as important considering most of us on here drive turbocharged vehicles.

Any back on topic.

Sure but if you consider the 'zaust post-turbo, I do not know for sure if insulating the system is going to make the car faster or slower.

I mean the hotter the 'zaust gasses the faster the flow rate but this in turn means it creates more friction and in turn more 'back pressure'.

Cooler 'zaust gases won't flow as fast (less volume) as so this means less friction and a lower 'back pressure' (although the gasses are denser but pressure loss is more effected by velocity than density)

Would be interesting to dyno some cars with and w/ & w/out 'zaust lagging.

Edited February 25, 2010 by Tony de Wonderful

[Tony de Wonderful]

on your power setup it wouldn't make a huge amount of difference. but should make it a touch quicker

Would you not need a re-tune?

[Tony de Wonderful]

actually they have tuned length headers. they have made the length of those pipes to the exact length that they need to make maximum power. they haven't just slapped on a few lengths of pipe to simple have the flames clear the engine block.

This is to do with pulse tuning rather than 'back pressure' per se.

[mad082]

Would you not need a re-tune?

not really. if the tune was done properly then it should still be well within it's limits, considering that people with the stock ecu more than double the low boost setting if they wind the boost up to 11 or 12psi, plus add FMICs and turbo back exhausts and the ecu still copes. in some cases they would be gaining close up to around 70kw over stock. any gain from dropping the exhaust off would be 10 or 15kw, which would be less than the difference between a cool winters night and a hot summers day

This is to do with pulse tuning rather than 'back pressure' per se.

yes i do agree with you there, however i was merely pointing out that they don't just have an open exhaust.

[noely1]

wtf this topic has got 6 pages of crap now??!

u guys are going to much in depth... should of kept it simple liek what others are saying; learn to drive the thing properly, take times on a reasonably cooler day and take into consideration its only a non turbo... not this coooler and hotter exhaust fumes crap tahts just bs that stuff really matters to those who actually have drag setup cars.. not dailys that jus wanna see how much thrashing there car can withstand!

[PM-R33]

Oh our discussion has nothing to do with this thread, i know that lol. This happens in the forced induction section all the time, we're quite used to it now. A simple thread about a BOV or something will turn into a great Engineering debate down to the complexicities of electrons and protons. Definetely keeps shit interesting

[noely1]

haha yeah true i spose it has filled my time reading every1's post's hehe

[bozodos]

so i have come to the conclusion that the OP's car needs MOAR JIGGAWATTS MARTY

[Tony de Wonderful]

What suffers more on a hot day? An N/A or a forced induction car?

It is forced induction right because intercooler efficiency is logaritmic with respect to ambient temp?

OTOH an N/A engines power decreases linearly with respect to ambient temp increase?

It's really hot right now and my car peformance really sucks.

[zebra]

yeah turbo car def suck the big one when its hot.

hence why im getting a big shiney flux capacitoy for my engine bay.

This sucks, I wrote an epic post abot the exhaust scavenging efgfects but sau died and my post went with it

but if people are confused when talking about EGTs and how they effect things then you would all hate me with what i wrote about. but ill give you a jist.

Note this has nothing to do with FI cars

The exhaust pulses travel down the pipes at the speed of sound, than hit the atmosphere and bounce right back up the pipe to the ports, you can time this so that once the pressure waves bounce off the exhaust port and open exhaust valve and can draw of the remaining gasses and draw in the air fuel mix.

Depending on the size and length of the primary pipes (headers) this can be tuned to a particular rpm range (tuned length extractors)

Now this is what they mean about not enough back pressure, to get thios to happen on a exhaust with mufflers is nearly impossible so the mid/tail diameter needs to be smaller to keep the velocity up, this isnt really a drama on modern EFI engines as they are a lot more efficiant and muffler tech has improved quite a bit. so no you wont lose and top end horsepower witha 4" exhaust on your exel, but you can lose low and mid range torque.

To build an NA race exhaust basicly consists of, get your primary pipes tuned to suit your cam specs comp ratio, valve and port size (+3mm radius larger than your exhasut port gives zero restriction without effecting gas velocity) and then dump it all into the biggest bloody exhaust you can fit under the car.

There was more but it is 7:15am

[Tony de Wonderful]

Now this is what they mean about not enough back pressure, to get thios to happen on a exhaust with mufflers is nearly impossible so the mid/tail diameter needs to be smaller to keep the velocity up, this isnt really a drama on modern EFI engines as they are a lot more efficiant and muffler tech has improved quite a bit. so no you wont lose and top end horsepower witha 4" exhaust on your exel, but you can lose low and mid range torque.

To build an NA race exhaust basicly consists of, get your primary pipes tuned to suit your cam specs comp ratio, valve and port size (+3mm radius larger than your exhasut port gives zero restriction without effecting gas velocity) and then dump it all into the biggest bloody exhaust you can fit under the car.

There was more but it is 7:15am

Stock cars don't come with tuned length 'zausts though do they? So going for a wider 'zaust (and less back pressure) should have no downside right?

Edited February 26, 2010 by Tony de Wonderful

[mad082]

actually stock headers are tuned length. they are tuned for low rpm torque and economy. aftermarket headers are tuned for top end power. anything designed for performance use isn't going have much time put into seeing how it will performs at 2000rpm with light throttle since no one on a track day is going to be coming out of a corner at 2000rpm in 4th gear when they could drop it back to second and accelerate much harder. performance headers have most of their tuning done around the mid to top end. that is why it isn't uncommon to lose a slight amount of fuel economy after fitting extractors if you only drive like a granny round town.

[Tony de Wonderful]

actually stock headers are tuned length. they are tuned for low rpm torque and economy. aftermarket headers are tuned for top end power. anything designed for performance use isn't going have much time put into seeing how it will performs at 2000rpm with light throttle since no one on a track day is going to be coming out of a corner at 2000rpm in 4th gear when they could drop it back to second and accelerate much harder. performance headers have most of their tuning done around the mid to top end. that is why it isn't uncommon to lose a slight amount of fuel economy after fitting extractors if you only drive like a granny round town.

Is that possible? I mean a stock manifold is shared rather than being a set of headers and you have a muffler (or two). Seems to me that would all screw up your pulses at any RPM?

[mad082]

how much exhaust gas do you think an engine is flowing cruising along at 3000rpm and maybe 10% throttle when compared to 7000rpm and 100% throttle? a hell of a lot less, that's for sure. that is why they can use a shared header system. the exhaust gas from all cylinders at light throttle is probably less than from 1 cylinder at 100% throttle.

[bozodos]

you can also get the 'collector' type and 'tri y' type extractors. only fags use tri y, 4 into 1 all the way for 4 cyl, same again for v8!

[Goodwin]

It's non turbo face it.

[Longz]

any idea what are the times for a GTR34 stock ?