Okay, for those of you who didn't know, I just drove my Z cross country from New Mexico to Connecticut without a scratch. (yeah, I gambled and got lucky!!). Along the way, I did a sea level retune on my built Z because I came from the "other mile high city" known as Albuquerque.

Comparison. Here's a great comparison between high altitude dynojet and a sea level dynojet.
To refresh you memory...
In Albuquerque (5500feet above sea level), at 17 psi, afr low 11s, timing being pulled 8-10 degrees...

Corrected SAE, 564rwhp
Uncorrected, 485 rwhp

In West Chicago (600feet above sea level), 17 psi, afr low 11s, timing 8-10 degrees

521rwhp!

So, for comparison's sake, the dyno jet in Albuquerque over corrected my numbers, HOWEVER, they were definately above the uncorrected amounts!!

After that little comparison, Charles tuned my Z for the following...

20 psi...~555rwhp consistent, with a peak of 569rwhp.
15psi....505rwhp
boost controller off, ~ 450rwhp.

Charles, please post one of my dynoes at high boost.

Thanks again Charles, you DA Mann!!

Ernie

 

 

Is this with the e-manage? If so, how do you monitor the knock sensor output to make sure that you're pulling enough timing?

Chris

 

can you tell us how much timing you pull on the new tune and what octane used ?

 

Ernie:

Your experiement PROVES that the turbo cars do not lose as much power as NA cars at high altitude!!!!! but then again, the corrected numbers were OVERcorrected..was charles' dyno a dynojet???

someone do some math here and come up with some ratios:

the dyno here overcorrected 8%

hmmm, still stand confused

we will never really know what the actual numbers are until a dyno tells us actual and not some guestimated actual based off of the inflated corrected numbers!

so, the mystery continues!!!! damn!!!!!

 

yummy




congratulations x569!!!!!

 

e-Manage right???

 

yes, he is using e-manage

 

Can you monitor the knock levels with the e-manage or are you just pulling out timing and hoping that it's enough?

Chris

 

The e-manage does not monitor the knock sensor, so you cannot be sure unless you use something in conjunction with the e-manage like the JS. I don't think this is the route you want to take, call me and I'll tell you why.

 

can you tell us all why?

 

YES tell us why.......

 

Thanks everyone for the props, I am an orphan right now in Connecticut until I buy my laptop this weekend. I will be online more afterwards.
I am using emanage as mentioned before and pulling about 8-10 degreees of timing as I think someone already mentioned.

 

You can monitor knock activity with many different devices. SAFC's, J&S, various scan tool devices.

Tuning is much more than A/F ratios and timing. It's a complete strategy....everything needs to be checked and monitored to optimize power AND safety across the board.

A challenge with tuning a built motor is that the knock sensor often picks up piston slap (stuff you cant even hear over the roar of the motor and dyno), and thinks its knocking, and pulls timing.

Most of the time, street tuning requires a little but more timing retard than optimal, to leave a safety cushion for the street. But if you pull too much timing, its actually equally dangerous..if not more dangerous than having too much. EGT's go through the roof if you retard timing too much. And all the while, your A/F ratios will seem safely rich. (timing retard lowers A/F ratios). The result is usually a melted piston or cracked ring land.

Tricky stuff....isnt it?

 

Can you briefly explain why too much timing retard raises EGT's? Since pulling timing allows the piston to travel more of the downstroke before igniting the A/F charge, I would think the less compressed charge would burn cooler, not hotter. Apparently, it is tricky stuff, because that seems quite counter-intuitive. Thanks Sharif!

 

a lot of tuning is counter intuitive.


going deep. are you pulling 10-12° straight across the rpm range, or varying by where you are at RPM wise? (for example pulling 13° @ low RPM and less at higher)

 

I believe less timing raises EGTs because the fuel is still burning and expanding in the exhaust stream. Hotter gas flows better though

 

if he tuned similar to me, then he is only pulling the most timing in the 4500rmp range--where it advances most aggressively...throughout the rest of the range, pulling gradually

TODD

 

Spark always initiates prior to TDC. If you timing is advanced 18 degrees, then the spark is fired 18 degrees BEFORE TDC. Since the flame front accelerates at a certain but predicatable rate (in a good tune), cylinder pressure will gradually increase, and reach its peak somewhere around 15-20 degrees AFTER TDC. So this explains why you need timing advance to properly run the car.

Now, lets say instead of 18 degrees of timing, you run 10 degrees. In this case, the compressed charge would not BEGIN burning until 10 degrees before TDC, so you have a highly pressurized charge that has begun burning way too late, and it ends up hanging around and burning up all the way through the power and exhuast stroke. So the end gases are SUPER hot....and very rich. They are richer than normal becuase they havent had a chance to burn completely....and that is why you can see very high EGT's but normal or richer than normal A/F ratios.

So there is a fine balance that has to be maintain on both ends of the spectrum. It's not just about setting an optimum A/F ratio...becuase there isnt one. It is just one component. But you can easily damage at motor at 11.0:1 with too muchy timing retard. Couple that with a slower burning 100 octane fuel and you have a blown torch inside your motor.

That's why I like to use both an EGT gauge, AND and wideband A/F gauge when tuning. That's my personal opinion.

 

It's doesnt advance more aggresively, as the ECU tends to settle in at WOT with 25degees of total advance.

At 4500rpm, you are near the trq peak, which translates into peak cylinder pressure. This is the area where you need the most timing retard, and then beyond around 5500rpm, you should gradually start adding in a few degrees of timing, to keep EGT's down, and flatten the trq curve, and keep power increasing power towards redline.

It's a really good idea to hook up an OBDII diagnostic tool that can view and log ignition timing, coolant temp, and other variables while tuning. It takes some of the guess work out of the equation....especially when using a piggyback type EMS.