hesitation when trying to blip

[MACK]

I am aware I have a powerloss since the dlv back box but I don't mind too much, the noise is worth the slight drop so that's fine, but it might affect something like the blip with all the gurgling and noises going on.. If an engine is a musical instrument, then....

Has anyone else noticed a drop in power with a fettled backbox or an aftermarket one? I've seen some chatter about this being a potential issue with a backbox delete but nothing about it also being an issue with modded backboxes or aftermarket ones etc
I really don't see how straight piping the backbox with the same diameter pipe as the rest of the exhaust would reduce gas velocity and consequentially effect scavenging etc. If anything the design of the standard backbox with its lack of any real internal piping would act as a restriction, reduce gas velocity and scavenging. Its not like folks are suddenly sticking a 4" full system on, so gas velocity is reduced

It’s probably going to reduce back pressure with a straight piped rear box which will have an effect on torque, there was a link on here a while back from M3 cutters where someone had dyno tested there car & found it 20-30bhp down with a modded back box :?
Rob

Interesting result, but that said the M3 backbox is piped entirely differently to a 3.0i/si as standard so I'm not too sure its a fair comparison. I did give this a lot of though before modding mine and personally I've always thought that the non M E85/6 backbox's lack of internal piping, with all the gases forced to travel through the wadding is primarily about noise reduction and that it actually causes a big restriction to gas flow so would damage exhaust gas velocity and as they're intrinsically linked scavenging/vacuum (or back pressure as its commonly know). At the end of the day the trick is to have pipework big enough to get all the gases out whilst maximizing gas velocity. Go too big and you screw this by slowing the gas velocity down

I guess if a modded back box is actually hurting performance in some way due to its straight through perforated pipe design then the same has to be said for the plethora of aftermarket backboxes out there as they all follow the same basic design principle.

 

[mjennings23]

I am aware I have a powerloss since the dlv back box but I don't mind too much, the noise is worth the slight drop so that's fine, but it might affect something like the blip with all the gurgling and noises going on.. If an engine is a musical instrument, then....

Has anyone else noticed a drop in power with a fettled backbox or an aftermarket one? I've seen some chatter about this being a potential issue with a backbox delete but nothing about it also being an issue with modded backboxes or aftermarket ones etc
I really don't see how straight piping the backbox with the same diameter pipe as the rest of the exhaust would reduce gas velocity and consequentially effect scavenging etc. If anything the design of the standard backbox with its lack of any real internal piping would act as a restriction, reduce gas velocity and scavenging. Its not like folks are suddenly sticking a 4" full system on, so gas velocity is reduced

It’s probably going to reduce back pressure with a straight piped rear box which will have an effect on torque, there was a link on here a while back from M3 cutters where someone had dyno tested there car & found it 20-30bhp down with a modded back box :?
Rob

Doesn't mean much unless they also have Dyno runs from the exact same Dyno in the same atmospheric conditions before and after the modification though, dynos are great at showing gains and losses if run before and after but beyond that, they're not accurate in any way scientifically.

For what it's worth I had my box changed, noticed no difference at all except the noise.

 

[MACK]

Has anyone else noticed a drop in power with a fettled backbox or an aftermarket one? I've seen some chatter about this being a potential issue with a backbox delete but nothing about it also being an issue with modded backboxes or aftermarket ones etc
I really don't see how straight piping the backbox with the same diameter pipe as the rest of the exhaust would reduce gas velocity and consequentially effect scavenging etc. If anything the design of the standard backbox with its lack of any real internal piping would act as a restriction, reduce gas velocity and scavenging. Its not like folks are suddenly sticking a 4" full system on, so gas velocity is reduced

It’s probably going to reduce back pressure with a straight piped rear box which will have an effect on torque, there was a link on here a while back from M3 cutters where someone had dyno tested there car & found it 20-30bhp down with a modded back box :?
Rob

Doesn't mean much unless they also have Dyno runs from the exact same Dyno in the same atmospheric conditions before and after the modification though, dynos are great at showing gains and losses if run before and after but beyond that, they're not accurate in any way scientifically.

For what it's worth I had my box changed, noticed no difference at all except the noise.

Very true.
Same here, the only difference Ive noticed is with my ears!

 

[road warrior]

to add to the mix im looking at the missing blip and reasonably sure thats a weak mixture, i have a clean exhaust but not a white one and,, without another to compare side by side.. as i listen to it ticking over i can detect sucking of air, a little bit of research shows there are many pipes that could be sucking in air, so where is the nearest e85 3.0i to me,(burton on trent) Neils is supercharged so hardly a comparison..
anyone ?

 

[road warrior]

also, back in thr day - crypton tuning could attach a lead and check for even firing - vaccum, compression ect and presumably mixture.. can carly do that ?

 

[MACK]

If you think you have an air leak on the 3.0i the rubber elbow that attaches to the throttle body has a little pipe as part of it. They're renowned for perishing and causing an airleak. That's where I'd start

 

[road warrior]

If you think you have an air leak on the 3.0i the rubber elbow that attaches to the throttle body has a little pipe as part of it. They're renowned for perishing and causing an airleak. That's where I'd start

thanks, got a pic so i can find it ?

 

[road warrior]

BEEN THINKING, the o2 sensor in the exhaust tells the computer what the mix is, if we increase the flow or back pressure maybe it will wrongly diagnose the richness.
on tickover my short term fuel trim stays around -3 to +3 - going to about 8 ish when i boot it - so not weak - i have also checked for any air or manifold leaks by spraying carb cleaner over the hoses and manifold and air box - nothin.. not so much as a flicker.
thoughts ? i suppose remapping it would work - any more thoughts or ideas ?

 

[road warrior]

thing is, i have absolutely no power loss or side effects on the 2.0.

 

[road warrior]

i tried something today and was amazed.. i stuffed a rag into one of the exhaust pipes, and it all went quiet - barely louder than the exhaust before it was dlv'd and then took it up the road, not only was it quiet but i swear it felt like there was less power ! i made a comment earlier about the exhaust being an instrument of sound - well it certainly sounds and feel like it.
I did to try and replicate/simulate how the untouched exhaust might be pressure wise. I tried both sides alternatively with the same effect and sound, with one side being slightly quieter than the other - so im happy to announce i unplugged it again for the glorious sound