Then how is SMART making more power with racegas on a 93 octane tune?

l8r)

 

B/C, as I said, the race gas in either of those scenarios allows the car to run in a lower row of cells on the SMART timing table. By running in a lower row of cells your car is running more timing, and by running more timing, making more power.

 

Ah, so the theory is that the engine noise floor is lower on race gas, and the off-the-shelf SMART timing threshold zero-line was measured on pump gas?

 

The mechanical noise floor should be the same on a motor whether it's running race gas or pump gas.

The difference is when comparing two different motors to each other. Every engine is different, but they should all be relatively close to each other. There is a thread where Shiv said that this smart timing table would not apply to a built motor... forged pistons, different compression ratio, lots of things can cause that noise floor to change.

My theory was this, his motor falls into one of these two catagories...



(I know, I rule at MSPaint )

The Blue line represents Shiv's "0" line of knock. This line corresponds to the amount of noise picked up by the knock buffer when there is ZERO knock actually occuring. Of course, you have to understand that this line is most likely an AVERAGE value from many cars that were tested during the development of SMART. You car COULD fall on that red line, or green line, depending on the engine. It COULD also be exactly on the blue line just as Shiv set up the SMART table to be.

Back to my thoughts on how his car picked up power on Race Gas.

In theory, if his engine's natural zero knock WOT noise was exactly corresponding to the Blue line (imagine that line going straight through all the Zero's on the SMART timing table) then at WOT with a tune that induces NO knock, SMART would not add or remove ANY timing.

Imagine the green line going through the row of cells corresponding to +0.5 degrees of timing on the SMART timing table, and the red line going through the -0.5 degrees timing.

Case A:

If his engine was one of the ones that fell on the green line, it being naturally quieter than Shiv's Zero line when at WOT and no knock, but his tune was slightly aggressive enough to induce enough knock on pump gas to put it back on the Blue line. When looking at the tune, it would look like a perfect tune because at WOT on pump gas, the SMART table would travel right along the Blue line like it doesn't have to pull any timing, and everything would be great. However, as soon as he put race gas in it would eliminate that slight amount of knock, and his SMARt timing table would then jump down to that green line that adds 0.5 degrees of timing through the whole RPM range. That might be enough for the 15HP difference, and it would appear that SMART is adding timing, when in all honest it really just stopped pulling timing.

Case B:

If his engine's natural noise did fall on the Blue line just as Shiv set up the SMART timing table. But his regular timing table tune was slightly aggressive for his car, and SMART was always pulling 0.5 degrees of timing, and his SMART table was always operating on the red line when on pump gas. He then puts in race gas and that slight knock is again, eliminated. His car then jumps down to the Blue line and essentially adds half a degree of timing, again resulting in a 15HP gain. (BTW, my half a degree corresponding to 15WHP is completely arbitrary)


In a perfect world...

His engine's natural noise would correspond to the Blue line, and his tune on pump gas would keep him on the blue line. Race gas would then do nothing... it can't eliminate knock that isn't there, and race gas can't change an engine's natural noise level. So NO power would be gained by putting in Race gas.

- Steve

P.S. - This is all at WOT!!!!

 

Hmm, I understand the theory, but here's what gets me:

1.) my zero line was dialed in by Shiv on the dyno, using 93 Octane, because I have a built 2.0l w/out balance shafts, so he changed the default zero line based on what we saw on the dyno.

2.) does SMART simply go to the zero line at WOT, or does it try to push past it? I had thought that SMART will try to add timing if it does not detect knock. E.g. on racegas the engine should not get noisier, even though more timing is being added.

Any clarification would be welcome.

l8r)

 

It will only add timing if it detects a level of noise below the zero line. So either your car got quieter since it was on the dyno, or maybe Shiv was conservative when he set the zero line. Either way, I'm now as stumped as you.

 

If you gained hp by just putting in race gas, then your zero line maybe too low. Plug a laptop in and do some map traces of the SMART timing map.

 

Excellent thread. I just bought a new Xede w/smart (Thanks VISHNU for the SALE!) and this thread was very informative.

p.s. Steve: your MS Paint skills are M4D TYT3!

 

Congrats on the purchase...

Yeah, I got the skillz...

- Steve

 

From what I've heard ..... timing advance via the timing table at WOT causes bad things to happen.

I would run a race gas map instead of hoping SMART will tune the fuel and timing. I dont think the SMART will actually bull 4% more fuel and possibly add in 3' of timing at WOT.

I could be wrong but I had bad luck adding timing to the timing table and I've never seen SMART yank out enough fuel for compensate for 104 octane.

 

True, but if your base timing table at those RPM points is somewhere around -2 degrees and the SMART timing table hits +1 degree then you're resultant timing is -1 degree. The Xede's output is still a net timing retard.

As far as the fuel goes, you're right....

- Steve