Dyno Scam?

**aeroengineer** · 12-09-2007, 04:00 AM

I was inquiring with the local dyno operator here in town the other day about his pricing on the dyno and a LC-1 kit. I mentioned that I might just buy the LC-1 and do my tuning on the stree, b/c I currently have light mods. He mentioned that I would not be able to get the car to use the enitre VE table on the street and that I would need the dyno to target the entire table. Here are my quetions....

1. His this guy BSing me to get some dyno business or is he shooting me straight?

2. Are LTFT averages with bolt ons, stock cam/heads typically linear across the entire VE table. I.e. can I get part of the table on the street and assume avg LTFT changes for the entire VE table

3. Do I need a 4th gear pull at WOT to adjust the PE table or can I do it in 3rd?

4. Will a tail pipe WBO2 sniffer work with Cats installed? Trying to figure if I can use his WB02 or if I need to install one in the Y? Using his might justify the cost of the dyno versus the LC-1.

Thanks for the input...

**Frost** · 12-09-2007, 04:55 AM

Originally Posted by aeroengineer

I was inquiring with the local dyno operator here in town the other day about his pricing on the dyno and a LC-1 kit. I mentioned that I might just buy the LC-1 and do my tuning on the stree, b/c I currently have light mods. He mentioned that I would not be able to get the car to use the enitre VE table on the street and that I would need the dyno to target the entire table. Here are my quetions....

1. His this guy BSing me to get some dyno business or is he shooting me straight?

2. Are LTFT averages with bolt ons, stock cam/heads typically linear across the entire VE table. I.e. can I get part of the table on the street and assume avg LTFT changes for the entire VE table

3. Do I need a 4th gear pull at WOT to adjust the PE table or can I do it in 3rd?

4. Will a tail pipe WBO2 sniffer work with Cats installed? Trying to figure if I can use his WB02 or if I need to install one in the Y? Using his might justify the cost of the dyno versus the LC-1.

Thanks for the input...

Here's a question for your tuner... If you *CAN'T* hit the VE cells on the street, why do they need to be adjusted? What is more real than running the car on the street after all? There is definitely part of the table that can't be reached, but it's not not an issue since it uh.... can't be reached

2. No.

3. 4th gear pulls are neccessary because the engine will run up at such a rate that the software can't get a good sample that covers the range of the pull. If tuning the MAF, it may take several 4th gear pulls to have enough complete data to make the change. If you are VE tuning (and/or keeping/calibrating the MAF) then there is no PE tuning. You set it to the AFR that you desire and modify the VE (and MAF) until it hits the PE target.

4. Depends on the dyno, setup, and more. I have seen a full half point difference from mine in a Y and the tailpipe O2 that goes AFTER catalytic converter(s). I have seen the two only vary a tenth or two as well. ....I know, not the conclusive answer you are looking for but it is what it is.

**vaticano** · 12-09-2007, 05:01 AM

i did mine on the street and was able to get most everything. the dyno will be better to use for timing changes to see what effect the changes made to hp.

reading AFR throught the tale pipe should show a bit leaner than pre-cat. i believe .1-.2
i tuned mine up to third gear, only because it is a bit reckless to go that fast on the street.
i hit most of my VE cells on the street, but there are some that you just wont hit. ie. high map low rpm.
not sure about the LTFT, mine are shut off for tuning.
maybe someone more knowledgable than i will chime in.

looks like they already did

**0rion** · 12-09-2007, 10:47 AM

about the only major plus to doing it on a dyno is not having to drive the car fast on the street. It's a real downside to doing it on the street. I live out in the country so I have less worries than some but it still bothers me doing all those high speeds on the roads.

I saw a difference in moving my wideband from the tailpipe without cats. I would assume it's due to leaks that I know are there but moving it up I saw a few tenths difference in AFR.

**aeroengineer** · 12-10-2007, 09:50 AM

Originally Posted by Frost

Here's a question for your tuner... If you *CAN'T* hit the VE cells on the street, why do they need to be adjusted? What is more real than running the car on the street after all? There is definitely part of the table that can't be reached, but it's not not an issue since it uh.... can't be reached

2. No.

3. 4th gear pulls are neccessary because the engine will run up at such a rate that the software can't get a good sample that covers the range of the pull. If tuning the MAF, it may take several 4th gear pulls to have enough complete data to make the change. If you are VE tuning (and/or keeping/calibrating the MAF) then there is no PE tuning. You set it to the AFR that you desire and modify the VE (and MAF) until it hits the PE target.

4. Depends on the dyno, setup, and more. I have seen a full half point difference from mine in a Y and the tailpipe O2 that goes AFTER catalytic converter(s). I have seen the two only vary a tenth or two as well. ....I know, not the conclusive answer you are looking for but it is what it is.

Thank you for the expert input. I was leaning the same way towards the "why" for the unobtainable cells, but this guy made it out like I would only hit 30% of the cells. From what Vaticano says sounds like he is exagurating a bit. I never thought about increased data logging resolution from a 4th gear vs. 3rd; excellent point and well taken.

You lost me a bit on answer 3 probably because I am a tuning cherry. I do plan on running the MAF (I want the atmospher comp.) an not a SD tune. If I understood G. Banish correctly I first need to calibrate the MAF, then adjust the VE, and finally tune PE for WOT (minus other work like AE/DE, etc.). Are you telling me that its either VE or PE and not VE & PE?

I have heard the same from others on the tailpipe answer. I think the only conclusive choice here is to do a WBO2 install into the Y to try and limit induced error.

I appriciate your expert adivice despite being counter to your business model.

V/r,

**aeroengineer** · 12-10-2007, 09:52 AM

Originally Posted by vaticano

i hit most of my VE cells on the street, but there are some that you just wont hit. ie. high map low rpm.

Good to know. As I wrote below the Dyno owner made it out to be that I would only about 30% of cells.

**aeroengineer** · 12-10-2007, 09:53 AM

Originally Posted by 0rion

about the only major plus to doing it on a dyno is not having to drive the car fast on the street. It's a real downside to doing it on the street. I live out in the country so I have less worries than some but it still bothers me doing all those high speeds on the roads.

I saw a difference in moving my wideband from the tailpipe without cats. I would assume it's due to leaks that I know are there but moving it up I saw a few tenths difference in AFR.

The street scares me a bit. 125+ even on a country road is pushing me into the nervous category.

**Frost** · 12-10-2007, 11:36 AM

Originally Posted by aeroengineer

....
You lost me a bit on answer 3 probably because I am a tuning cherry. I do plan on running the MAF (I want the atmospher comp.) an not a SD tune. If I understood G. Banish correctly I first need to calibrate the MAF, then adjust the VE, and finally tune PE for WOT (minus other work like AE/DE, etc.). Are you telling me that its either VE or PE and not VE & PE?

People fuel tune in lots of different fashions. The one closest to what you describe, the VE must be tuned before the MAF. You setup your injectors, force the car into SD, and tune the VE. After that, Set the EQ in the PE table equal to something safe for start, like 12.4-12.6:1 NA but make it a flat line. Then re-enable the MAF and plot the error of commanded vs. actual AFR. This error is applied back against the MAF table until the trims are inline and you are hitting commanded AFR at WOT. This doesn't take long at all (MAF cal). Then on the dyno, set your PE to the AFR you command for WOT fuel tuning rather than fudging up PE for WOT (old method).

Good luck.

**aeroengineer** · 12-10-2007, 12:36 PM

Originally Posted by Frost

People fuel tune in lots of different fashions. The one closest to what you describe, the VE must be tuned before the MAF. You setup your injectors, force the car into SD, and tune the VE. After that, Set the EQ in the PE table equal to something safe for start, like 12.4-12.6:1 NA but make it a flat line. Then re-enable the MAF and plot the error of commanded vs. actual AFR. This error is applied back against the MAF table until the trims are inline and you are hitting commanded AFR at WOT. This doesn't take long at all (MAF cal). Then on the dyno, set your PE to the AFR you command for WOT fuel tuning rather than fudging up PE for WOT (old method).

Good luck.

Got it. Its starting to become clear.
Thanks

**Frost** · 12-10-2007, 03:06 PM

To be more clear, the reason that you have to do this (tune in this order) is that when the MAF is connected and working, almost all fueling comes from it. The VE is referenced in bits in transitional throttle (simplified model for this post) when the MAF is working. Also, unless changed, ALL fueling over 4K RPMs comes from the MAF.

Depending on your level of modifications, there are other options for tuning if keeping a MAF, like lowering the point that the car moves from VE/MAF blend down to ranges lower than 4K RPMS for example...

**aeroengineer** · 12-10-2007, 05:19 PM

Originally Posted by Frost

To be more clear, the reason that you have to do this (tune in this order) is that when the MAF is connected and working, almost all fueling comes from it. The VE is referenced in bits in transitional throttle (simplified model for this post) when the MAF is working. Also, unless changed, ALL fueling over 4K RPMs comes from the MAF.

Depending on your level of modifications, there are other options for tuning if keeping a MAF, like lowering the point that the car moves from VE/MAF blend down to ranges lower than 4K RPMS for example...

So if I set up SD and tune VE do I use LTFT to bring each VE cell closer to stoch? I am thinking a target 0 or slightly negative FT value is better so that PCM can command more fuel in case of lean condition. Do I need to consider STFTs or is that more of an instantaneous change that will eventually be represented in LTFTs?

When reviewing commanded vs. actual WOT values is this difference represented by a % differnce and then multiplied to the corresponding MAF calibration value? I assume this is where the WBO2 comes into play to verify actual AFR. If I follow you correctly, I am shooting to get the MAF cals such that the commanded = actual at WOT. That way I can the proceed input commanded values in the PE table as necessary to achieve MBT/HP on the dyno.

Thanks again for all of the advice.

**Frost** · 12-10-2007, 05:36 PM

Originally Posted by aeroengineer

So if I set up SD and tune VE do I use LTFT to bring each VE cell closer to stoch? I am thinking a target 0 or slightly negative FT value is better so that PCM can command more fuel in case of lean condition. Do I need to consider STFTs or is that more of an instantaneous change that will eventually be represented in LTFTs?

When reviewing commanded vs. actual WOT values is this difference represented by a % differnce and then multiplied to the corresponding MAF calibration value? I assume this is where the WBO2 comes into play to verify actual AFR. If I follow you correctly, I am shooting to get the MAF cals such that the commanded = actual at WOT. That way I can the proceed input commanded values in the PE table as necessary to achieve MBT/HP on the dyno.

Thanks again for all of the advice.

That's pretty much it for the most part. THough if using FTs, I would just use STFTs (disable LTs) and drive a LOT to get an accurate average. I might use FTs to touch up cruise areas, but they are pretty worthless to tune by. You can't approach any high load conditions tuning with them, and once you use a wideband you will be upset that you ever wasted so much time with FTs. Since you need it for WOT anyway, you just as well get it to use on the rest of the tune. Depending on level of mods and what type of tune, there times that I just leave the STFTs active and not the LTs.