I know the best WOT tuning is accomplished on a Dyno. However, those of us who do not wish to use a dyno either for cost reasons or for our own enjoyment of tinkering as we go, is there a viable alternative?
For instance. What if you were to make consistent 3rd gear WOT pulls from 2500 - redline and adjust your timing, fuel, etc until you see the quickest time between various rpm ranges. Takes a bit of time and would have to be on same stretch of road each time etc. Why would this not be a realistic alternative to a dyno session? I mean unless you are after the almighty dyno number for bragging rights, would this method not be just as effective?

Your Thoughts??

 

Can and has been done. Most logging softwares allow the ability to log airflow, RPM, fuel consumption, calculated torque, etc (elapsed time over the same mph sweep is good). Something to measure the difference. Best place to do this is the drag strip of course as an increase in MPH usually indicates an increase in overall horsepower/ assuming launch variables are the same (many times I've gone to a test and tune day and just "hit it" at the same rpm point, aka a roll out to the 330' or something).

Software such as Virtual Dyno can get you very close as long as you calibrate the settings correctly.

 

Virtual dyno is a good tool for this. But for best results you need to keep the variables to a minimum. Use the same stretch of road.... possible do 2 runs, 1 in each direction and take the average if that area is windy. You can even guesstimate the weight differences between full gas tank vs 1/4 tank etc in the input fields.

It's a good tool but you need to control to variables if you want consistent useable data.

 

Awesome thanks you guys. I will be using HP tuners scanner when I try this out. It can be configured to give all the relevant information to make the proper adjustments. Being responsible as to where you perform such tests is important I know. I am 50 years old and have been into fast cars since I was 14.

 

I tuned my Subaru that way, and was happy with the results (got 377whp on a dyno later, which is typical for the mods it had), and now I'm in the middle of re-tuning it the same way (now with bigger cams, ported heads, etc, hoping for 400-425). I am not sure it's a good plan for a naturally aspirated car. But I'm also not sure it isn't. I just wonder, and I hope someone can shed some light on this.

With pump gas and full throttle pulls from 2000 RPM to the rev limit in an LS1 / LS6... is spark advance limited by knock, or do you have to watch for power to level off or drop off to know when you've advanced it far enough? I ask because from data logs on the road, I found it pretty hard to get a series of pulls where the virtual dyno shows the same power back-to-back with enough precision to really use that data as a guide for tuning decisions.

My Subaru, being forced induction, was very much knock limited, so I basically just picked a reasonable AFR table, found the knock threshold up and down the rev range at various boost levels, and then backed off a couple degrees... and that worked jut fine. If an LS1 / LS6 is also knock-limited through the whole rev range at full throttle, then that approach should work for these cars as well.

If it's not knock-limited, then you'll need a way to plot power over RPM with pretty good precision in order to know when you've reached or passed MBT (or when you've gone too rich / too lean, if you're also tuning AFR for power, or trying different AFR/spark combinations to see what's best). If you have a very flat very smooth road for very consistent pulls, then maybe that's do-able, but I didn't have much luck with it.

I'd love to hear how you folks approach tuning these things.

 

This basically.

Nearly all turbo / SC applications will be knock limited on timing advance. You make the best torque at the point of knock because the cylinder pressure or temperature prevents further advance.

Most NA engines will be knock limited at some RPMs but not others. So you can't just map the ignition until its knocking a little as you can for the boosted example. You can go 'over the hill' with ignition advance and not realise.

This is why a dyno will give you better results, if used correctly on an NA engine.

 

I had mine street tuned a handful of times and it's fine to do it that way but not everyone is willing to run their car to 160 on the street, you should use 4th gear though if the car is a 6 speed and not 3rd

 

Oh, right... one of the things that makes street tuning practical with my Subaru is perfectly reliable traction in 2nd gear. Full throttle pulls through the whole rev range are no problem and it barely goes over 60. Then I do 4th gear pulls in the lower half of the rev range to get into cells that 2nd gear can't reach, and still barely pass the posted limit.

Why does 3rd gear vs 4th gear matter?

 

Actually it would matter more on your TC application. The engine will see significantly more load in the higher gears. Also much higher in-cylinder and turbo temperatures which in turn will affect safe spark timing and lambda ratio. For NA probably not much in it, although you get better residency (time spend at given RPM and load) to check knock and fueling.

 

Yeah, I'm quite aware of the effect with turbochargers.

I'm curious why (whether) it matters with NA cars.

I should have been clearer about what I was asking.

 

You can definitely tune using 3rd gear pulls. The first couple yrs of my shop in the mid 2000's, I tuned solely on the street (before I bought my dyno). I had a stretch of unoccupied road, no traffic hardly ever, straight, etc. I honestly thought my world would open even more once I bought my dyno, but frankly it really didn't, in some ways it was just more work. A lot of shops get in to the cycle of doing wide opened throttle tuning only, and turn and burn. Being on the street allows you to tune with real aerodynamic loads, plus you get a lot of the drivability sorted out on the low end. As you put in timing, you can see burn characteristics change, leaning the mixture, and you basically can tune the ignition timing accordingly, while updating your fuel.

Dyno's use 4th gear due to 1:1 ratio, but on the street it's not critical.

 

Why it is that 1:1 ratio critical on a dyno?

The crank:wheel ratio just ends up being 3.42:1 because of the diff gears...

 

I agree a dyno tune is best only used on a dedicated race application where the RPM's rarely drop below 4500----A street tune is far better as it addresses idle/part throttle/ and WOT tuning
You can acheive the same data info doing a street tune to dial in your WOT fueling and spark timing\
Just to get accurate readings the trans must be in a ratio closets to a 1:1 ratio On an A4 trans this is 3rd gear----If you take fuel and spark readings when the trans is over driven it is not accurate as there is not sufficient load on the engine--- To go a step further you must also use a "wideband 02 sensor"
as the stock narrowband 02's are not very accurate depends on how much you want get to that last 5-10 RWHP Using the narrowbands just error on the side of rich to be safe--Typically if you use the narrowbands you would want the 02 voltages to have a max reading from .900 to ,925 Millivolts
This would approx get you a WOT AFR of a safe 12.5-1 ( the narrow bands don't read in AFR ratios on a data logger but in millivolts) The higher the number the richer it is---
Now if you choose to use a wideband as they are far more accurate i would consider a safe AFR reading of about 12.7-1 for the street and hot rodding

 

You seem to imply that a narrowband can be used "somewhat" and of course thats not so...unusable for tuning aside from cruise/idle....it's a switch basically, nothing more. Narrowband is far too erratic to log or do sh*t with.

I definitely tuned forced induction setups richer than 12.5:1 on the street; that's more the N/A target you're speaking of. I went high 11's on FI for piston crown cooling and a margin.

 

I tune on the street and track, and all my cars and customers cars are running quicker than vehicles with similar or identical setups. Must be doing something right

Dynos are fun and all but you can't replicate the same real world conditions found on the street/track. I deal with guys who prefer timeslips over dyno sheets.

 

"To go a step further you must also use a "wideband 02 sensor"
as the stock narrowband 02's are not very accurate "
This is EXACTLY what I said---So I cannot see where you can infer that I said the narrowbands are accurate with boost or highly modded engines--- The only time I use narrowband readings is in a totally STOCK engine with only bolt ons not including either shorty or LT headers
Data logging with EFILIVE will give you tremendous 02 readings Most importantly The "average 02 readings" Which you want to be between .400 and .550 millivolts to get you a Stoich of 14.68-1 at P/T
and then at WOT only in the gear ratio that s closets to 1:1 you would want the voltages to have a max of about .875 to .900 to get a WOT reading of about 12.5:1 a safe street AFR
The modern day narrowbands are far superior than in the past AND on a bolt engine with NO headers YES their readings are very close and safe for a street hod rod--

 

Somebody needs to plot the response of the front O2 sensors against a wideband to put this subject to rest.

There was a time when if someone said wideband or narrowband that told you everything you need to know about an O2 sensor. That hasn't been true at least since my 2005 Subaru was made. I have no idea whether it was true in the C5 production era, but a plot would settle the question.

 

Handful of times I've correlated WB to NB and maybe +/-20mv... around 850mv = 12.5AFR for me. 900mv is way too rich for my NBs.

I tune my mildly modified track car on the street... 3rd gear is fine, just target 0.25 richer. Depends on fuel if you can tune by KR, 91oct in 90deg ambient... sure, you'll see knock before MBT. 93 in the heat likely, cool prob not... maybe stay close to factory deducts. I run E30 mix and target a curve based on researching other's maps and my experience with 91... I've never seen KR on E30, but I'm fairly conservative keeping car on track rather than HP.

 

If you really had to tune with NBs without any WB reference you could
populate VE or MAF in the lower ranges using stoich
once tune is within few %, can open loop at 12AFR to get your NB setpoints then tune the upper and WOT.

 

I am in the middle of tuning my car now as I just installed a SC....I am getting part throttle pretty close but I need the dyno for WOT tuning. I simply do not have roads available to tune WOT, not to mention the ones I do have have pot holes and dips and car is LOW...I am looking forward to my dyno