Is this boost "normal"?

[Jester B]

I did a few pulls with a VAD-Mobile today and graphed the results.

Car is a 2001.5 S4 Tip running OC.t Stage 1

3 Graphs attached. What I am wondering about is the "lag" behind the requested boost and the actual boost delivered. And, on the 2nd graph...the "spike" of actual boost after I've lifted off. Is this normal, or is there something to be looking at?

No, I don't have a boost gauge in my car.

[Jester B]

Re: Is this boost "normal"?

No one? Jordan? Kyle?

[R_Ethug]

Re: Is this boost "normal"?

jeff you want to buy one of my gauges.. i have a VDO in a precutout vent ready to go you just need an install kit .. 50 bucks

or a AWE ver1 no vent tho.. you'd have to do it yourself (not hard at all)
50 bucks

then you need an install kit from C1 or somewhere.. easy as pie!

[Jester B]

Re: Is this boost "normal"?

Thanks Ryan, but I don't want a gauge. Just someone to help interpret the graphs...

[R-Audi]

Re: Is this boost "normal"?

If you are looking at any mods (including your chip) you should have a boost gauge for maintenance purposes. UNless you are constantly logging.. its a must.

A spike after you let off the gas is definitely NOT normal...that being said
These logs are kinda useless... you've gotta use third gear, and go thru the entire powerband... that way its consistent.

[p951]

Re: Is this boost "normal"?

I think what Jeff was asking is specifically if the lag is normal, and if the boost spike at the end (when he closes the throttle) is normal in these cars.

These logs are not useless, Jeff is not testing for total boost, or if the boost is falling off at higher rpms, he's just asking if the lag is normal or not.

Basically asking if there looks like there is a problem with the wastegate (no there isn't - the boost builds and holds), or with the recirculating valves (if they are closing properly, or if the diaphragms are ripped and letting boost leak back into the intake of the turbos, and if they are opening quickly enough to let the excess boost pressure flow back, not stall the turbos when he lifts off the throttle).

I don't think that there is a major problem, although the recirculating valves look like they may be tired (ripped, well used) which I would suggest to him to check.

[R-Audi]

Re: Is this boost "normal"?

IF there was a problem with a wastegate or 710 it would be more visible via a complete log...

Sure you can see the initial build, and spike after letting off.. but A complete RPM log is better at seeing that and any other problems that may exist.

[Smarty39]

Re: Is this boost "normal"?

I agree with Mark...although the graphs are not completely useless, they would be much more useful if they were 3rd gear, full-band pulls. Just by looking at the graphs you posted, there really isn't much to see as that spike could be caused by many things. But, if it were a full log, it would be easier to speculate what may be wrong. As always with these cars and boost issues, you can always check the dv's and wastegate lines...if have a couple brand new 710N's sitting around if you need them...

PS - Jeff, were you at Cirque de Soleil last night? Or, was it just one of the other 50 silver S4's around town lol!

[Jester B]

Re: Is this boost "normal"?

Nope, not me at Cirque. Have heard the show was good, though.

Will try the 3rd gear pull if that is what is needed. Had a couple of codes when I got back from vacation, but they have not come back yet. Everything is probably just fine.

Out of curiosity, how hard is it to change the O2 sensors?

[Smarty39]

Re: Is this boost "normal"?

The show was actually much better than I expected...I would highly recommend it

O2's are not too terribly bad, but that doesn't mean they don't suck either lol. Make sure you get a crow's foot socket and take your time...do you need to change the primary or secondary?

[R-Audi]

Re: Is this boost "normal"?

The primary sensors SUCK! well drivers side that is.. passenger isnt bad.

[R_Ethug]

Re: Is this boost "normal"?

hahha jack! yea kyle i was at cirque on the weekend! freaking amazing! i'm going to everyshow they bring .. a little $$ but well worth it just don't buy the pop/popcorn for 50 bucks and sneak stuff in

[The_Jerbel]

Re: Is this boost "normal"?

Jeff,
Sorry, I've been on holidays for the last week or so.
You may have a small boost leak, as the boost ramp is a little slow, but not out of the normal range. You probably have a torn DV causing your boost spike when letting off the throttle. If you replace the DV's and the spike still occurs, then you should test the N249 valve.

[Jester B]

Re: Is this boost "normal"?

Thanks, Jordan.

What I noticed as well is the little vacuum line between the diverted valves was quite loose and frayed. When moved back in place, everything feels much stronger. I need to replace it.

Is there a good place in town to get the euro style hose clamps with the rounded edges?

Still plan to redo the log in 3rd as suggested.

[R-Audi]

Re: Is this boost "normal"?

I think you are looking for Oetiker Clamps.. Pain in the ass. For the vacuum lines.. just use zip ties, or if you are really worried worm clamps. While you are at it you might as well replace the lines.. its dirt cheap vacuum line from any NAPA etc..