My boost pressures seem to be elevated. Peak is 1.68 bar (24.69 psi) tapering to about 1.60 bar (23.6 psi).

I didn't think the stock turbo was capable of sustaining that level to redline. I have verified the same boost pressure with two separate gauges and a Blitz FATT DC II.

Mods are Stage 1+, 264/272 @-2/-2, Helix DP, Random Tech 3" Cat, Vishnu Sig Series Cat-Back, MR DV, and Samco Intercooler hoses.

Wastegate duty cycle (table 4) shows 100% across the board. Shiv tuned car back in October and only change since then is from 65mm HKS DP to the Helix 3".

I get the same boost level when using the generic Stage1+ 93 octane w/Xede flash map. It just takes longer to get to max boost, but when it hits 100% duty cycle it shows the same boost levels with minimal taper.

Has anyone had to use less than 100% wastegate duty cycle to control max boost above 5k rpm?

Could there be a mechanical problem with my boost solenoid or waste gate actuator?

 

Well, cold weather will make your car show alot more boost.. I think those numbers sound about average for this time of year. Maybe some others can confirm this.

 

Has anyone had to use less than 100% wastegate duty cycle to control max boost above 5k rpm?

sure plenty, also my FATT isnt really a BAR reading I think the actual conversion is 14.5 psi/1.0 on that gauge which corresponds to our dyno gauge pretty well. IIRC I dont have time this sec to look for sure though

 

Thanks for the response David. I understand that the FATT may not be accurate. That is why I used two other mechanical gauges to verify readings. They may not be accurate either, but I tend to believe that between the three of them my boost is too high.

How much should I reduce the duty cycle table percentages to get it back to the 22 peak and 19 taper?

Thanks

 

That does sound too high at the top John...
take the 100's down to 92....if boost remains the same you will know you have a wastegate/actuator problem...

 

Thanks Andrew,

I thought it was too high also. I tweaked it a bit today dropping the duty cycle to 95.3% from 3-4k, 96.9% from 4.5-5k, and 98% from 5.5-7k. This brought me back to around 22.6 psi peak and tapering to 21.5 or so.

I'll do some more tomorrow to get it back down to not more than 20psi above 5k.

 

I see that you live in NoVA. Last night on 495 I saw 27~28 PSi on pump spike in that 30D weather. I was a bit scared but the cold weather will usually put 2 psi on top. You are fine dont worry

 

Az3AR,

I agree with your observation concerning the effects of cold weather on peak boost pressures. However, my 24+ psi peak was of sufficient duration for me to feel it was more than a transient spike. I kept that map stored in Bank 0 so it remains available at the flip of a switch. New map for daily winter driving is tuned for 22 psi max tapering to 20. I really need to get a set of det cans so I won't be so paranoid about the effects of elevated boost levels. In the mean time I prefer to be safe rather than sorry.

 

jfh,

If i'm not mistaken you can also use an OBDII logger. It won't log absolute timing with the Xede, but ignition retard is ignition retard whether it's absolute or an offset of one. Anyways, just an idea...

 

you could always do what ez76 does - just run 100 octane

I too have noticed increased boost levels with the cold. Have you changed anything since your last tune?

 

knock be not proud

 

sorry John!

 

Meanmud,

Only change since last tune was replacing the HKS 65mm DP with 3" Helix. It's under control now with new wastegate values in Table 4.

What is the purpose of the additional bleeders that Shiv uses on some cars? Mine doesn't have any installed, just the hoses (with pill removed) from relay to actuator.

 

When I went catless, I had the same effect. What DV are ya using?

 

MR DV