Boost before and after N249 bypass

[rsmith]

Hello all,

just looking for your comments, i did a log this morning and noticed my Boost was fluctuating up and down at around 19 to 20 psi, i did two logs one before the n249 nypass and one after, the run after seems to have a more smooth boost curve.

Comments are welcome, i plotted the boost to a graph using the measuring block 115 template on the Ross-tech site, i can post the actual logs if anyone would like that.

Also what would cause the boost to drop a few PSI and then gain it again?

Before.

After

 

[GlanzaV]

Hi mate - I had my (very stock) AMK LCR 210 Rolling rodded at the weekend. Made a respectable 220BHP.

Quite interested to see if any of the boffins out there can answer why the boost flutuates? On my first power run the boost was a fine smooth curve, second run it dropped by a couple PSI and then regained further up the rev range, similar to your graph above. Obviously I never had the advantage of plotting requested vs actual though!

Looking at your first graph my only answer would be that it's a bit of a feedback loop - It peaks, the valve shuts, opens, shuts etc... and gives you the fluctuation?

Thanks for the bypass how-to as well!

 

[Ape]

Nice one for posting the graphs, confirms my thoughts on the Bypass that it does hold boost better etc.

Very useful info is this

 

[GlanzaV]

Only noticed after my post it hadn't been commented on since last year though!

 

[Ape]

Another good spot, amazing what diamonds you find in the rough

 

[rsmith]

Another good spot, amazing what diamonds you find in the rough

Cheers.

Only noticed after my post it hadn't been commented on since last year though!

yeah posted this ages ago as part of my n249 bypass guide I did, tbo honest mate we would need to logs of your power runs before we could speculate what is wrong, if anything that is, Dodgy n75 can give screwy boost readings, again though logs would show better

 

[ibizacupra]

Hi mate - I had my (very stock) AMK LCR 210 Rolling rodded at the weekend. Made a respectable 220BHP.

Quite interested to see if any of the boffins out there can answer why the boost flutuates? On my first power run the boost was a fine smooth curve, second run it dropped by a couple PSI and then regained further up the rev range, similar to your graph above. Obviously I never had the advantage of plotting requested vs actual though!

Looking at your first graph my only answer would be that it's a bit of a feedback loop - It peaks, the valve shuts, opens, shuts etc... and gives you the fluctuation?

Thanks for the bypass how-to as well!

heat

 

[GlanzaV]

Bill, I asked that as they had the blowers quite close to the front of the car (Obviously concerned about the flow into the SMICs) but he said that they blow at about 80-90mph which for the gear and RPM would be more than the actual airflow along the road? Which seemed plausible to me!

Secondly do the lambda sensors up the exhaust measure correctly for VAG cars? Mine was said to be running a touch lean, and another RR I was at all the SEATs were told the same? Will post the graphs later if they'd help.

 

[leon cupra r]

Has anyone else noticed that the request has changed between the two as well? I don't think the bypass can be put down to being the sole reason for the changes in boost + delivery ...

 

[rsmith]

Has anyone else noticed that the request has changed between the two as well? I don't think the bypass can be put down to being the sole reason for the changes in boost + delivery ...

its not about boost increase more-over boost flucuation.

 

[leon cupra r]

its not about boost increase more-over boost flucuation.

Surely it is the N75 + Wastegate that has the precise control over boost though? Not the DV which is surely either open or closed - it can't be 'pulsed' or indeed regulated by N249 - it can be opened but can't be forced back closed...

I really struggle to see how having the N249 disconnected has any effect on boost - if the DV is closed, its closed. If it's open, you wouldn't just be loosing a couple of psi...

The only way I can see the N249 being connected/disconnected having any effect on boost is all the pipework taking time to pressurise? I wouldn't mind seeing repeat logs, and also logs done on a few different cars to see whether it is just a coinsidence that there were less fluctuations...

 

[rsmith]

Surely it is the N75 + Wastegate that has the precise control over boost though? Not the DV which is surely either open or closed - it can't be 'pulsed' or indeed regulated by N249 - it can be opened but can't be forced back closed...

I really struggle to see how having the N249 disconnected has any effect on boost - if the DV is closed, its closed. If it's open, you wouldn't just be loosing a couple of psi...

The only way I can see the N249 being connected/disconnected having any effect on boost is all the pipework taking time to pressurise? I wouldn't mind seeing repeat logs, and also logs done on a few different cars to see whether it is just a coinsidence that there were less fluctuations...

get on google and start to read what the n249 actually does.

 

[leon cupra r]

I know what the n249 does - it opens the DV at ECUs request. No need for the sarcastic reply?