133 UNDERPOWERED

[msjm6747]

put the oem induction set up back on this evening and it already feels better

 

[DanPaul7]

You should get another dyno printout now, quite curious how much it actually made you lose :s

 

[msjm6747]

yeah i want one too, but for a good one there all like 50 /60 quid ago

 

[benmc]

I've made power on my open cone filter but getting a good cold feed pressure have worked better too

 

[msjm6747]

I've made power on my open cone filter but getting a good cold feed pressure have worked better too

have you got pictures of your open cone setup with cold air feed ??

 

[maggi200]

I have an open cone. I don't care if I've lost a billion horse power. It sounds nice. And if I wanted lots of ponies, I'd have bought Something fast(er)

 

[msjm6747]

I have an open cone. I don't care if I've lost a billion horse power. It sounds nice. And if I wanted lots of ponies, I'd have bought Something fast(er)

i agree with you, if my car was running book figures i wouldnt mid losing a few to have the nice noise but because im running so low on power im trying to rake back every horse i can

 

[Martin_172]

Btw Martin all that s**t about n/a needing back pressure is a load of bull.. You need the right sized exhaust diameter to create a pressure so it flows most optimum... I.e you have a little flow of water In a big space the water is going to trickle slowly if you add more to the flow you will hit an optimum flow rate to the size if a pipe then once over the optimum rate your going to create a back pressure which is bad ....

and do you have an ECU controlling fueling and ignition on your little flow of water?

when building an engine that is going to be mapped for maximum peak power then of course you want as little back pressure as possible, during your power band. but when your talking about a road car then this is not completely the case. Back pressure is always a product of fitting an exhaust that is designed for more than just peak power.

take a clio 197/200 for example and replace the centre silencer with a straight through pipe, and suddenly the car has a nasty nasty flat spot in the bottom end of the rev range, now this silencer is of course post lambda so the only thing possibly effecting engines power is back pressure? so in your opinion what else could be causing that? since of course the need for back pressure is bull....

 

[benmc]

The silencer disturbs the flow and the car was set up to that, with a straight through pipe the actual size maybe wrong like you say the cars been designed with them, straight through pipes would improve the flow but maybe too wide so a smaller diameter pipe might be better straight through , your right in saying with silencers a back pressure will be caused but that's generated enough pressure to get optimum performance flow with that sized pipe, I had a 197 too and I removed the pre cat and centre silencer and yea flat spot was bad if the diameter was smaller to improve flow it would have reacted better, and ecu and lambda is just part of a closed loop control system... Change your water flow to blowing through a tiptop drink straw, a McDonald's straw and a wrapping paper tube and notice how the back pressure on small one is bad coz you can't get rid of enough, mc Donald's is better, and wrapping paper tube you struggle to create a good flow through ...

 

[MovingShadow]

I thought back pressure was more needed on cars with turbo's than on NA engines?

 

[Martin_172]

turbo cars depends on the setup, if you have too little back pressure on certain turbos/wastegates you can get issues with boost spikes.

but generally the less back pressure you have after the turbo the quicker it can spool up and reach its maximum boost level.

 

[singlespeed]

Thinking of the extreme scenario of a very restrictive exhaust, the pistons will be pushing exhaust gasses into the exhaust manifold (as expected). If the gasses can't escape then pressure will biuld up in the manifold and by the time the inlet valves open the overpressure would try to get out of the inlet.

Being as theres valve overlap and sound wave pulses going up and down the exhaust system, you can't treat the removal of a silensor and droping some back pressure as the sole reason for a flat spot. you would also need to consider how the induction pulse is also affected for the overall change in breathing. If the cylinders dont fill with the same amount of air/fuel by the time the valves close to start the compression stroke then you will get less power

 

[Martin_172]

I would have imagined the cylinders are always going to fill with the same amount of air though as the engines sucking it in, the only difference is how quickly the engine can suck it in not how much it can actually suck in? I may be wrong on that though

 

[BikNorton]

Being as theres valve overlap and sound wave pulses going up and down the exhaust system, you can't treat the removal of a silensor and droping some back pressure as the sole reason for a flat spot. you would also need to consider how the induction pulse is also affected for the overall change in breathing. If the cylinders dont fill with the same amount of air/fuel by the time the valves close to start the compression stroke then you will get less power

I read something about that on motoiq, I'll try and dig it out.

Thats interesting, where abouts in the country are you? Wonder if it varies in quality across the country?!

I'm in Manchester, filled up at the new massive Tesco by Salford Quays - brand new station. I suppose they might not have cleaned/dried the tanks properly. At least when the O2 sensor problem occurred it was almost completely restricted to the south-east because the fuel came in down there.

 

[BikNorton]

Here's the headers article I mentioned in the above post which goes on about pulse tuning and stuff.