AccessPort + Stage 2 91 Octane Map + Spare ECU = ...

[Dean]

To use a quote many of you will not remember from an old Robin Willams routine...

"Instantly well hung."

My STX map was good, but now the car has some serious kahones. I'm sure a SS custom ECUTek map would be better(Kevin), but this only required a 10mm socket, and about 20 minutes. And it's as smooth as butter...

Did the quick multiplier bump trick as well.

I contemplated using the 93 octane map to compensate for the altitude, but decided not to.

Wonder if Nate has time to do a pull or three on Thurs. AM. it would be interesting to see what it is really doing.

Nows alls Is bes needsing is a topwatch and St.Tuner Yo!

[MattR]

So this new setup is legal in STX?

[MikeK]

Sweet! Are you going to get the tuner software now?

[MikeK]

Originally Posted by MattR

So this new setup is legal in STX?

They have an STX legal map, but the standard map has modified boost, so no.

[Nick Koan]

Or, more what I assume, is that Dean plans to swap the STX legal mapped ECU back into his car, and leave the AP flashed one at home on AutoX days.

[Dean]

Originally Posted by nKoan

Or, more what I assume, is that Dean plans to swap the STX legal mapped ECU back into his car, and leave the AP flashed one at home on AutoX days.

Right you are Ken....

Or at least that's the plan. I could flash the real time STX map down on it, but I'm not convinced it is really legal to at least the intent of the rules.

Right now, I'm just going to have fun with it at Laguna and driving around.

Haven't ordered the street tuner SW yet...

[MattR]

Eric is working with his Street Tuner right now...He's on his way to get my stock air filter to put the intake back to stock. I'm intersted in seeing his results.

[Kevin M]

Originally Posted by Dean

To use a quote many of you will not remember from an old Robin Willams routine...

"Instantly well hung."

My STX map was good, but now the car has some serious kahones. I'm sure a SS custom ECUTek map would be better(Kevin), but this only required a 10mm socket, and about 20 minutes. And it's as smooth as butter...

Did the quick multiplier bump trick as well.

I contemplated using the 93 octane map to compensate for the altitude, but decided not to.

Wonder if Nate has time to do a pull or three on Thurs. AM. it would be interesting to see what it is really doing.

Nows alls Is bes needsing is a topwatch and St.Tuner Yo!

More boost = more betta, at least comparing stock maps.

93 won't really do anything for you without a 93 high-altitude map. You're not knocking on the 91 map presumably, so no need for higher octane until you get the Street Tuner. Then you can give a tiny bump in boost and play with fueling a bit and spark a lot.

[Dean]

Originally Posted by BAN SUVS

93 won't really do anything for you without a 93 high-altitude map. You're not knocking on the 91 map presumably, so no need for higher octane until you get the Street Tuner. Then you can give a tiny bump in boost and play with fueling a bit and spark a lot.

No, I was thinking of runnnig the 93 octane map in place of the 91 map I am running even though we only have 91 octane up here. I thought better of it, but my initial thinking was that the higher altitude more than compensated for the lack of octane.

What I don't know is if the ECU reads absolute or relative pressure. Heck, I'm not sure what my gauge does.

If I am boosting to 15-16 PSI absolute, then I definitely don't want the 93 map.

But if I am boosting to 15PSI relative, then the 93 map might be OK.

[Kevin M]

There's no difference between absolute and relative "boost." If your gauge says 15 psi, presuming it's accurate, than your manifold is getting atmo+15 psi. I think what you're really asking is, does your MAP sensor read absolute (atmo+boost in bar) or relative (just boost). Everything I've read indicates you always want to read absolute, so I would expect the AP tune to be doing so.

[Dean]

Originally Posted by BAN SUVS

There's no difference between absolute and relative "boost." If your gauge says 15 psi, presuming it's accurate, than your manifold is getting atmo+15 psi. I think what you're really asking is, does your MAP sensor read absolute (atmo+boost in bar) or relative (just boost). Everything I've read indicates you always want to read absolute, so I would expect the AP tune to be doing so.

Oh n0es, I sense a Dean vs. Kevin battle coming on... I'll swerve and see if I miss it....

OK, I wasn't thinking. Boost gauges are relative, that is why they have negative and positive numbers. there is no such thing as negative absolute pressure. Vacuum squared?

The feed from the AP/ECU is the same and matches the gauge wery well by the way. This also makes sense since the target boost range for the stage 2 maps is "15.8psi +/- 0.5psi", and this is the neighborhood I'm seeing despite being at altitude. So the boost map is likely based on relative pressure.

The MAP on the other hand is probably absolute as you said since I would bet that is what the fuel map is tied to.

If I only had a graphing calculator.... and the energy to go look up the equations, I could figure out what 15.8PSI at 4500feet vs. sea level is.

That lack of extra pressure is why I thought I could get away with the 93 octane map since most likely the primary difference is timing advance.

Anybody with a turbo and stock boost up here could probably run 89, or even 87 octane and not notice the difference. It might actually improve performance now that I think about it.

let the banter ensue...

[Kevin M]

Try not to raise boost too much up here. Remember that pressure ratio is what determines compressor efficiency, not relative boost. So making 15 psi at 4500 feet gives you less air into the IC which is also hotter than at sea level.

IIRC (could be a bit off) normal atmospheric pressure in Reno is about 13 psi, so you're well over 2.0:1 at 15 psi. Probably still well within range of the turbo below 6000 rpm.

I would expect the 93 octane map to have both more boost and more timing advance. Both Cobb, Vishnu, EcuTek, and myself will tell you, always map for YOUR parameters. If you aren't running 93 or 100 octane, don't use those maps. Same goes for 89 and 87- I wouldn't use 87 at all, but there's probably an 89 map that will work fine up here.

Anyways, the 93 octane "stock" map from the Cobb site won't really help you. You are making all the safe power you can on 91, so the differences between the 91 map and 93 map will only cause knock, which robs power, or simply make less power in the first place. When you get the Street tuner, you can sort of ignore that, and use whatever you want as a base map and find the "wrong" spots, but I'd still start with a map meant for the octane you're tuning on.

[Dean]

Actually, 15.8 PSI is the target for 91, and 93 maps, though I guess it could vary by RPM. I bet that is a compressor issue, not an octane issue. doesn't the stock turbo drop off significantly above 16PSI at sea level?

On a bigger turbo, I would agree that you could run more boost on 93 than 91 and make better power than just bumping timing might. In this case, I bet most of it is timing bump though.

I guess we could get Eric to look at the maps since he has ST.

And I agree, with most of your omments, that is why I am running the 91 map.

[Kevin M]

I would expect a small increase in boost on higher octane (we used to tell people 16.5 psi max at vishnu) but Cobb might have used the same boost map for simplicity/safety. I don't think eric's ST can read normal AP maps until you marry it to the ECU.

[MikeK]

FIGHT FIGHT FIGHT!!!

Here is a chart of pressure drop vs altitude for standard temperatures ... charty goodness ... however, turbochargers can compensate for this pressure drop by forcing more air in, so you will not see that kind of pressure drop like an n/a car would.

When I was hanging around at cobb waiting for them to finish my install, I asked them about this, and they said at SLC altitude, which is within a few hundred feet of Reno, they see about 0.5 psi less boost than sea level, so for Reno their stage 2 target boost is about 15.3 +/- 0.5 psi.

[Kevin M]

Originally Posted by MikeK

FIGHT FIGHT FIGHT!!!

Here is a chart of pressure drop vs altitude for standard temperatures ... charty goodness ... however, turbochargers can compensate for this pressure drop by forcing more air in, so you will not see that kind of pressure drop like an n/a car would.

When I was hanging around at cobb waiting for them to finish my install, I asked them about this, and they said at SLC altitude, which is within a few hundred feet of Reno, they see about 0.5 psi less boost than sea level, so for Reno their stage 2 target boost is about 15.3 +/- 0.5 psi.

Pressure ratio, pressure ratio, pressure ratio. 15 psi up here is not the same as 15 psi at sea level. As I said, you get less, hotter air up here than say, in Sac. For reasonable maps, it's not such a huge issue at midrange because the turbo is still pretty efficient. It mostly manifests itself at higher RPM, where the CFM you're flowing doesn't work so well with the PR you're aiming for.

Thanks for the chart, that's helpful.

[Dean]

I told you I needed a graphing calculator....

So based on the Charty numbers:

( 14.69 + 15.8 ) / 14.69 = 2.08:1 @ Sea Level

( 12.46 + 15.8 ) / 12.46 = 2.27:1 @ 4500 Feet

OK, and with good old pvnrt, we have less, hotter air... Even at 15.3 it is still less hotter air.

Now with less air(CFMs), shouldn't the intercooler be more efficient(or maybe that is a bad word) More able to reduce the temperature of that given volume assuming sufficient cooling of teh intercooler itself?

But with less air, slightly hotter or not, we have less pressure at or before combustion/detonation, so thus, less octane required... Or so was my understanding.

[Dean]

P.S. I hate when these OT threads turn technical...

[Kevin M]

Originally Posted by Dean

OK, and with good old pvnrt, we have less, hotter air... Even at 15.3 it is still less hotter air.

Less boost at a given altitude and temperature is always less air, just a bit cooler. More boost gives you more power at all altitudes until you hit the point of uncontrollable knock.

Originally Posted by Dean

Now with less air(CFMs), shouldn't the intercooler be more efficient(or maybe that is a bad word) More able to reduce the temperature of that given volume assuming sufficient cooling of teh intercooler itself?

Yes and no. Lower boost makes it easier for the air to flow through the IC, but the lack of air molecules flowing over the outside of the IC makes the cooling efficiency worse. Double whammy from the altitude when you're trying to compaensate for the atmospheric pressure.

Originally Posted by Dean

But with less air, slightly hotter or not, we have less pressure at or before combustion/detonation, so thus, less octane required... Or so was my understanding.

Yeah pretty much. See, "high" boost pressures require more timing advance than "low" boost pressures, because the flame front moves faster the higher the cylinder pressure is (more molecules bumping into each other more often at higher speeds = faster checmical reactions). Because the flame moves slower at lower boost making less power, MBT is not as high numerically. Reduced ignition advance allows for a lower octane gasoline. that's why I would think it would be pretty easy and safe to make an 89 octane commuting/economy map for use up here. Run like 13 psi and keep your AFRs around 11.5-12:1 and you should be able to run 89 all day long, even at full throttle.

[Kevin M]

Originally Posted by Dean

P.S. I hate when these OT threads turn technical...

Turnabout is fair play.

[Dean]

Stupid question... Does A/F sensor = O2 sensor? or is there actual something that can tell gas vapor from all the other components of air?

[Kevin M]

AF=O2 sensor. AF ratio is calculated by how much O2 is left in the exhaust I believe (never really looked up the exact chemistry used). Don't trust the stock "wideband" too much though. It reads poorly below 13:1 and not at all below 11.3:1.

[Dean]

Originally Posted by BAN SUVS

AF=O2 sensor. AF ratio is calculated by how much O2 is left in the exhaust I believe (never really looked up the exact chemistry used). Don't trust the stock "wideband" too much though. It reads poorly below 13:1 and not at all below 11.3:1.

Where is the optimal location for a wideband 02? Up Pipe?

[Kevin M]

Wideband location isn't as critical as EGT placement. Uppipe is most common for O2 sensors, although some people htink they belong in the downpipe for some reason.

[tysonK]

So Dean basically you like the higher boost.

Sounds logical more power is nice.

Nice enough for some poeple to say screw STX I want to have fun in street mod, and not worry about changing ECUs and stuff.



edit: TSTX