Club Touareg Forum banner

521 - 540 of 565 Posts

·
Premium Member
Joined
·
6 Posts
So....further update for you. I went driving last night ( it was nice and cool like 67 ). No power drops at all. Car pulled fairly well in normal, and did ok on the highway. I hadn't really tried it much before with the tune... popped it into sport mode on the highway and it jumped from 65 to 85 like it was nothing.... and tried a low rpm pull in sport mode and it's almost ridiculous the difference between that and normal now.... before the tune there was a little difference but not much for me. Now its worlds apart....... I'm suspecting that what I actually need is to upgrade the intercooler.... I'm guessing the temps are getting way to high and its pulling timing and etc.... I also need to get a TCM tune. I can get easily 3 - 5 mpg better in below 60 mph driving by shifting in manual mode and keeping the rpms low.... stupid diesel gate tcm tune keeps them high way too often....... hope you figure yours out!
 

·
Registered
Joined
·
2,004 Posts
You guys running tunes in hot climates should look at your IATs.... might be a good time to start considering upgrades to your SMICs or looking into converting to a FMIC, etc.
 

·
Registered
Joined
·
218 Posts
You guys running tunes in hot climates should look at your IATs.... might be a good time to start considering upgrades to your SMICs or looking into converting to a FMIC, etc.


It’s been in the low to mid 90’s without about 88-100%(it’s been raining) humidity. Think the intercooler upgrade is going to be needed.
 

·
Registered
Joined
·
218 Posts

·
Registered
Joined
·
2,004 Posts
IMHO, unless you're willing to do a serious FMIC, I would consider water\meth injection prior to upgrading the SMICs.... but I haven't seen any IAT logs from anyone comparing how much better the Porsche SMICs work compared to ours......

You could also venture into the propane injection world, but once again, we are starting to discuss some serious mods here....
 

·
Registered
Joined
·
218 Posts
IMHO, unless you're willing to do a serious FMIC, I would consider water\meth injection prior to upgrading the SMICs.... but I haven't seen any IAT logs from anyone comparing how much better the Porsche SMICs work compared to ours......



You could also venture into the propane injection world, but once again, we are starting to discuss some serious mods here....


Think that would only be an option for me if I went with Yrktreg’s hybrid turbo. Right now the Malone pulls like a beast on the highway which I drive the most and I’m happy with it. I had a Snow that I never installed on my Z and the system looked pretty straight forward. A couple people I know had some pretty sophisticated settings for the meth when tuning.... crazy stuff.
 

·
Registered
Joined
·
176 Posts
Because lower RPM = more MPGs....... if you had more torque output between 1500-2000 rpm, your TCU wouldn't drop several gears to keep things moving along.....

Stock ratings were


This is why all along, we have been discussing getting more torque faster and making it last longer, instead of peak values in parts of the powerband that would only get touched during hard acceleration, etc......

If you could have max torque from say 1500-2500 rpm, there's a very good chance that wall you're pulling around would be more convinced to follow along..... know what I mean?
Not true at all. Load dictates MPG's. Cruising at 3k rpms with no load would yield higher MPG than cruising at 1500rpms with 100% load.

In fact, here's an engineering conversation on this matter using nearly exactly the same terms as I used above:
 

·
Registered
Joined
·
2,004 Posts
Not true at all.
Sure bud.....

You should spend some time reading and comprehending the same link you're correcting us with.... just sayin.....
P.S. This is from an actual Engineer in an F1 team..... hopefully you don't tell me F1 guys don't know what they are doing next.....

Here's a quick sample. (exert)

Peter Hewson McLaren Racing said:
In general, fuel consumption will always gets worse with speed, due to the increasing mechanical and pumping losses. This is why you should always drive your car in the highest gear that the engine can comfortably manage. A further complication with diesels is that the flame speed is limited (which is why no diesel does more than about 5000rpm). So high engine speeds are a very inefficient way to operate diesel engines.......
There's lots more detail presented in his post as shown below.....

........This is contrary to your finding, so there is a need to look deeper. As with most engineering, the real answer is in the detail. You give no indication of the torque profile of the engine. Being a small diesel engine it is very likely that the peak torque potential at 2650rpm is very much higher than it is at 3000rpm (for the reasons of gas flow efficiency and flame speed mentioned above). If everything else was the same then a first order assumption is that fuel consumption (in 'volume per time') is proportional to the power being developed. If the engine is developing more power at 2650rpm than it is at 3000rpm then it would not be surprising if it was using more fuel at the lower speed. In fact, the only way it could use more fuel at 3000rpm would be if the efficiency of the engine fell at an even faster rate than the rate of reduction of the engine power. Such situations can occur with poorly tuned diesels, and the result tends to be huge amounts of smoke (unburned hydrocarbons) being expelled from the exhaust. As other have mentioned, check the specific fuel consumption, not the absolute fuel consumption, then calculate the efficiencies. You should find that the engine is significantly more efficient at lower rpm, even if absolute fuel consumption is higher at lower rpm.
There is also another possible explanation: If the engine is designed to operate efficiently at 3000rpm (and many are, because it coincides with the 50Hz used for AC electricity etc), then the engine may be tuned to be efficient only at 3000rpm, and may over-fuel massively at 2650rpm because the governor is trying to raise the engine speed back to 3000rpm. This tells you nothing about engine efficiency, and is symptomatic only of the specific governor tuning of the engine in question.
 

·
Registered
Joined
·
176 Posts
Nice job cherry-picking one reply out of the 30 replies in there that most closely represents your agenda. Most of those other ~30 replies all go hand in hand and completely disagree with your assertion.

My personal experience in owning 7 diesels has also proven worse economy in low rpm, high load situations, with economy always improving in higher RPM shifts with low load.

How many diesels have you owned, out of curiosity?
 

·
Registered
Joined
·
2,004 Posts
My personal experience in owning 7 diesels has also proven worse economy in low rpm, high load situations, with economy always improving in higher RPM shifts with low load.

How many diesels have you owned, out of curiosity?
2 TDIs and I still own them.... (my 2010 DD has only seen a mechanic for a timing belt change because I wanted to use up my dealer credit..... all other maintenance\fixing has been done by me in my driveway during all of its life)
Did you read what we were discussing above?...... It was towing (so the load isn't vanishing at any engine speed). The fact of the matter is, you need to be in the engine's power band to do it as efficiently as possible.

And if an F1 Engineer's input aligns with "my agenda", I'm OK with that.
 

·
Registered
Joined
·
176 Posts
Because lower RPM = more MPGs....... if you had more torque output between 1500-2000 rpm, your TCU wouldn't drop several gears to keep things moving along.....

Stock ratings were


This is why all along, we have been discussing getting more torque faster and making it last longer, instead of peak values in parts of the powerband that would only get touched during hard acceleration, etc......

If you could have max torque from say 1500-2500 rpm, there's a very good chance that wall you're pulling around would be more convinced to follow along..... know what I mean?
Nah ah ah, you said lower rpm = higher mpg, and that's just not true, even if you didn't clarify in your post that you mean while towing.

Ever hooked a scan gauge up while towing? It will never register higher mpg when lugging the motor out. When you ride rpm higher there is less load, lower duty cycle, less boost and lower consumption every time.
 

·
Registered
Joined
·
2,004 Posts
Ever hooked a scan gauge up while towing? It will never register higher mpg when lugging the motor out. When you ride rpm higher there is less load, lower duty cycle, less boost and lower consumption every time.
So what you're saying is that I've been driving my Jetta around for the last 259k WRONG???..... instead of shifting below 2k, I should be holding redline to pickup more MPG? Interesting.
 

·
Registered
Joined
·
600 Posts
Discussion Starter #534
Oh boy. About to jump into this one....

What matters is the system as a whole. In general higher engine speed increases both frictional losses (mechanical interface between the rings cylinder, and bearings of crank, cams, lifters etc...) and the fluid pumping loses. The gearbox losses, accessory scavenge losses and the turbo efficiency. All of this translates to a measured BSFC under a particular operating state. It is entirely possible for a particular powertrain install to have more than one peak efficiency operating point depending on the state conditions under evaluation.

It isn’t a simple answer.

I’ve found on my MK4 BEW that 4th fear sometimes yields better mileage than 5th gear depending on speed, altitude, grade and humidity. Without parametric dyno test data it is tough to know exactly. But I bet a datalog from the ECU could help one determine BSFC and best operating range.

Towing with my Touareg with a brick of a trailer demonstrated staying in the early part of the torque band yielded the best efficiency and MPH. A look at the dyno curve shows why operating at peak torque is slightly better than peak power.
 

·
Registered
Joined
·
176 Posts
So what you're saying is that I've been driving my Jetta around for the last 259k WRONG???..... instead of shifting below 2k, I should be holding redline to pickup more MPG? Interesting.
Which pump, rotary? Unit injection? Eh, it doesn't matter. I'm not saying to redline your car for maximum efficiency, but I've noticed consistently shifting low always resulted in poor economy (and acceleration..) vs running it up a few thousand RPM. Every car is different, every motor, final drive ratio, pump type, turbo type yadda yadda yadda. So, as a generalization, better economy is indeed achieved riding the rpm's a few thousand out vs short shifting, lugging etc.
 

·
Registered
Joined
·
600 Posts
Discussion Starter #536
It’s all a function of staying in the peak torque portion of the torque curve.

It would be interesting to compile a torque vs rpm vs BSFC data set and map it to a 3D plot. It would put this issue to rest.
 

·
Registered
Joined
·
176 Posts
So....further update for you. I went driving last night ( it was nice and cool like 67 ). No power drops at all. Car pulled fairly well in normal, and did ok on the highway. I hadn't really tried it much before with the tune... popped it into sport mode on the highway and it jumped from 65 to 85 like it was nothing.... and tried a low rpm pull in sport mode and it's almost ridiculous the difference between that and normal now.... before the tune there was a little difference but not much for me. Now its worlds apart....... I'm suspecting that what I actually need is to upgrade the intercooler.... I'm guessing the temps are getting way to high and its pulling timing and etc.... I also need to get a TCM tune. I can get easily 3 - 5 mpg better in below 60 mph driving by shifting in manual mode and keeping the rpms low.... stupid diesel gate tcm tune keeps them high way too often....... hope you figure yours out!
Just as an FYI, you typically want to let the new ECU 'settle' for 1-2 weeks before making any comparisons or dyno followups. In every single instance of car that I've tuned, there is a 'settling' period (in varying days by every vehicle) where the ECU has to some how get acclimated to the new tune/hardware etc. I'm sure that the cooler air added some power (depending what air temp was on dyno day vs that 67* day you spoke of), but likely the ECU settled in AND the cooler air temps are the difference you were feeling. If you were to re-dyno it right now with zero other changes, I bet those numbers are even higher.
 
521 - 540 of 565 Posts
Top