[OpenFlash]

Originally Posted by hotrod182

Massive low end torque is great for driveability if it is easy to modulate with the throttle. Hence a similiarly powered E55 will usually kill a V10 M5 at the dragstrip. My 335d with 500+ Tq is effortless in launching and cut and thrust traffic.

A big question I have is besides the huge power/Tq differences in the normal driving range below 4000rpm. The dynos show what the turbos are doing under a load. How does this correspond to transient response? If you are driving around town, and let off the thottle in 1500-4000 rpm range, to slow down, and then speed up again. What is the difference in reaction time before you get boost again? Is the single not only weaker in output, but also taking much longer to hit that weaker output? This would represent non-dyno situation, or where we don't have an opportunity to power brake the car in a planned encounter.

If you are in the 2500-3500rpm range, the car will pull as strong as a stock tunes n54 which is hardly anemic. But if low RPM power is what you want, this particular single turbo isn't for you. Those who will use it will understand and accept the fact that a downshift will be requires to light up the tires. That's the compromise one makes to have a 3 liter 600whp daily driver. This car will run 10s in DD trim so I'm not sure one would call it an underperformer in the real world.

[jpsimon]

did that sensor come in yet today?

[son_of_siggy]

Originally Posted by hotrod182

Massive low end torque is great for driveability if it is easy to modulate with the throttle. Hence a similiarly powered E55 will usually kill a V10 M5 at the dragstrip. My 335d with 500+ Tq is effortless in launching and cut and thrust traffic.

A big question I have is besides the huge power/Tq differences in the normal driving range below 4000rpm. The dynos show what the turbos are doing under a load. How does this correspond to transient response? If you are driving around town, and let off the thottle in 1500-4000 rpm range, to slow down, and then speed up again. What is the difference in reaction time before you get boost again? Is the single not only weaker in output, but also taking much longer to hit that weaker output? This would represent non-dyno situation, or where we don't have an opportunity to power brake the car in a planned encounter.

Not quite sure I get your question. To an extent, the turbos should already be somewhat spooled as you're just coming off a higher RPM/situation where you've seen boost. If you've let the motor wind down to 1500 RPM, they'll obviously be spinning slower than if you just let off at 4k and decided to get back into boost.

Your main concern seems to be off-idle capabilities below the 3k range based on your many posts criticizing the single turbo. Stick with your twins if it's such a big deal to you. Sure, most people don't spend a lot of regular driving time above 3k rpm. But most people also know when they'll be in a situation requiring boost and can pre-shift accordingly. Even with the auto it takes a mere few seconds to drop down the 1-2 gears needed to get your engine into the power making range. How often do you find yourself with a spontaneous race where you simply didn't have time to get up to 3k rpm? I understand that off-idle power is fun, and for those who think its MORE fun than what a single can provide, stick with the twins.

Yeah, I get its an open forum and people can post whatever they want, but who are you really trying to convince that the single is a bad idea?

[OpenFlash]

Originally Posted by jpsimon

did that sensor come in yet today?

Yes indeed. Going to pick it up from the dealership shortly. Should have it calibrated and functional sometime next week.

[import36]

Originally Posted by shiv@vishnu

Yes indeed. Going to pick it up from the dealership shortly. Should have it calibrated and functional sometime next week.

that's when the real witchcraft happens!

[hotrod182]

Originally Posted by son_of_siggy

Not quite sure I get your question. To an extent, the turbos should already be somewhat spooled as you're just coming off a higher RPM/situation where you've seen boost. If you've let the motor wind down to 1500 RPM, they'll obviously be spinning slower than if you just let off at 4k and decided to get back into boost.

Your main concern seems to be off-idle capabilities below the 3k range based on your many posts criticizing the single turbo. Stick with your twins if it's such a big deal to you. Sure, most people don't spend a lot of regular driving time above 3k rpm. But most people also know when they'll be in a situation requiring boost and can pre-shift accordingly. Even with the auto it takes a mere few seconds to drop down the 1-2 gears needed to get your engine into the power making range. How often do you find yourself with a spontaneous race where you simply didn't have time to get up to 3k rpm? I understand that off-idle power is fun, and for those who think its MORE fun than what a single can provide, stick with the twins.

Yeah, I get its an open forum and people can post whatever they want, but who are you really trying to convince that the single is a bad idea?

Just trying to quantify the loss down low in everyday driving situations. Sounds like with the manual, Shiv says its perfectly liveable, which I believe. Will be great if the automatic testing goes well also. This is all very important information for those adopting single turbos in the future. By all means, not just questions regarding Shiv's particular setup, more just the driveability comparisons of singles in general. I'm sure many people are still interested in responsiveness and driveabilty in their DD cars. My questions are probably also applicable for big turbo developments on the N55.

On a side note, do you have a newer CTS-V? Perfect example of a very torquey engine. When you change the pulleys on those cars and gain HP without loosing low end power, its a win-win situation. If you knew you were going to loose half your power in the 2000-3000 rpm cruising range would you still do the upgrade to gain 150hp in the upper power range? I mean, yes, it would be great to have the upper HP, but I would suspect many CTS-V owners would miss their "exceptional" low end torque/responsiveness if a mod cut their cruising hp/tq to 50% levels. Just a hunch. Again, in a race car, of course driveability is not a concern. On the forums..every says..what the heck, of course its a trade off. But in reality...time will tell when more people evaluate and drive the single turbo setups. I figure they are perfectly liveable, but you will probably be losing one of the most exceptional characteristics of the stock turbo's powerband. The low end grunt.

Believe me, I don't drive like a Grandma, I would say I drive harder than 99% of the people on this forum. But believe it or not, for a DD, I still place high value on driveability, cruise efficiency, etc. But maybe my point of view is a more rare one.

[jpsimon]

It's simple. 100% of the people who get a single turbo are getting it for big power... not because they only want to frolic around town at 1-3k rpm picking daisies all day. You have options though, the smaller of which will give you full boost a lot sooner yet still make a good amount more power than upgraded twins.

Your comments sound like there are going to be a bunch of people (who don't know what a turbo is) with guns pointed at them forcing them to upgrade against their will.

[bimmertt]

Originally Posted by hotrod182

And don't get me wrong. I don't drive like a Grandma, I would say I drive harder than 99% of the people on this forum. But believe it or not, I still value driveability, cruise efficiency, etc. But maybe my point of view is rare?

I think this is reasonable. I just think back to the infamous "29.2" software release. Holy hell, this place blew up like a christmas tree because no one liked the lag. However, like others have already mentioned, there is a very significant power advantage with the single turbo which will make the trade-off worth it for most.

[Fundahl]

Originally Posted by shiv@vishnu

Yes indeed. Going to pick it up from the dealership shortly. Should have it calibrated and functional sometime next week.

[hotrod182]

Originally Posted by bimmertt

I think this is reasonable. I just think back to the infamous "29.2" software release. Holy hell, this place blew up like a christmas tree because no one liked the lag. However, like others have already mentioned, there is a very significant power advantage with the single turbo which will make the trade-off worth it for most.

Good observation. I am actually hoping singles are very successful, and of course very interested/concerned about things like powerband, etc. It also makes sense to avoid the complexity and cost of a big cfm custom twin turbo setup. And I am hoping the same traits that benefit the N54 Single will eventually be adopted to a custom N55 setup in the future.

[Kris 335i]

Originally Posted by jpsimon

It's simple. 100% of the people who get a single turbo are getting it for big power... not because they only want to frolic around town at 1-3k rpm picking daisies all day. You have options though, the smaller of which will give you full boost a lot sooner yet still make a good amount more power than upgraded twins.

Your comments sound like there are going to be a bunch of people (who don't know what a turbo is) with guns pointed at them forcing them to upgrade against their will.

Exactly. The people doing the single turbo will be doing it for the big top end power. I absolutely love the low end torque of the N54 (especially with meth ) but I know I would love 600WHP even more .

[rader1]

There are things you can do tuning wise to help with spool-up. With the smaller turbo and the right tune lag might not be a big problem.

[Das Stig]

boost is only a downshift away

[son_of_siggy]

Originally Posted by Kris 335i

Exactly. The people doing the single turbo will be doing it for the big top end power. I absolutely love the low end torque of the N54 (especially with meth ) but I know I would love 600WHP even more .

And that's exactly the point. It's not like anyone has made claim that people won't lose some of the low end torque. I guess I'm just seeing a lot of redundant posts about it like it's something people aren't aware of or expecting.

Hotrod - Actually the CTS-V I had was the older model when I signed up on these forums. That said, I currently am driving a boosted Saleen, so I understand what you mean about the torque. But that's an entirely different animal altogether, given that both cars are V8's that are relatively torquey anyways.

I think most people looking forward to the single fully accept what the implications are below 3k rpm, and are prepared to alter their driving habits when needed to enjoy that extra top-end power. Having 500whp at 1500 rpm is fun, but not fully usable. I'd gladly give some of that up to get more to pull me along in the higher ranges. First/second will still be fun and go by quickly, just in the latter halves.

[Carl Morris]

Originally Posted by hotrod182

On a side note, do you have a newer CTS-V? Perfect example of a very torquey engine.

If you want the feel of a big supercharged V8, then you should buy one. It's a very different thing from a small(er) big-turbo motor.

[Skydive]

The O2 sensor "issue" has more to do with approach than anything else. In you're flashing the DME for your single turbo tune you don't need to place the lambda sensors pre-turbo, because there is a software "switch", but if you don't know where to find the switch, or you prefer a piggyback tune, the best way to deal with the issue is with the Innovate fittings in your manifold, as Vishnu have done. So far, there are no flash offerings... but I can say with a fair amount of certainty that as the single-turbo offerings broaden a bit, lambda sensor relocation will be optional.

[Sniz]

Originally Posted by jlh335i

Sniz, I was waiting for you to post haha. Your e36 is sweet.
I remember reading your build thread awhile back... do you have any more videos to show off an inline with a big turbo ?

thanks man.

I actually drove a long way out of my way to the gym this afternoon trying to a little tuning on my Aquamist system, traffic was terrible.

I tried to take a video at normal cruising speeds to show the responsiveness on a lower compression i6 with a now 'antiquated' gt35r. of course my smart phone thought it would be smart to have a hiccup right when I got on the gas in 5th gear.......

for reference I would normally be in 3rd gear to get max acceleration.

what i was trying to show is that if you have the engine cruising at least 3,000rpms its very responsive, below 2,500 its no champ though. from 2,500-3,000 it is still very powerful.

this is at a power level a good ways under what shiv has developed, much lighter car though.

[805beemer]

Originally Posted by Skydive

The O2 sensor "issue" has more to do with approach than anything else. In you're flashing the DME for your single turbo tune you don't need to place the lambda sensors pre-turbo, because there is a software "switch", but if you don't know where to find the switch, or you prefer a piggyback tune, the best way to deal with the issue is with the Innovate fittings in your manifold, as Vishnu have done. So far, there are no flash offerings... but I can say with a fair amount of certainty that as the single-turbo offerings broaden a bit, lambda sensor relocation will be optional.

Are you guys still on schedule to have a working prototype soon. End of march if memory serves me right???