Turbo spool

[hhrfreek]

I have a ZFR 6758 and running e47 on my Solstice. What is the "standard" for measuring turbo spool? For example, I start a 3rd gear pull at 2500rpms and by 3700rpms I am at 20psi. By 3900 I am at 24psi. I am asking because I think I should be able to spool up a 6758 quicker than that right? Should I be checking spool differently? I like the high rpm boost, but I really miss that nasty spool from the K04. This turbo doesn't seem like a huge advantage unless you boost 24psi+ because essentially I just moved the power band and I am hesitant to run more boost on stock pistons so I may not take full advantage of this turbo till then.

[JimmyS]

I run a WR3 (EFR6758) on e47 on my Sky and I've never really thought about spool time but my tranny is an auto so comparing spool times on mine versus your manual trans is like comparing apples and oranges. I run 27-28psi but I'm also close to 4000 feet here.

I never had the chance to run any comparison runs (like 40-115 or 60-100) on the stock turbo with HP Tuners vs the bigger turbo since I upgraded the turbo and changed from Trifecta to HP Tuners in the same week though it would have been nice to have those comparisons. I recently replaced the factory Eagle F1 tires with Michelin PSS's and on the factory tires, they would spin/roast at will anytime I went WOT below 50mph due to the downshift and quick hit of power so that's part of the reason that I've never really been concerned with spool time. With the Michelin's, they hold the pavement well and don't really break loose unless I'm around 35mph or below.

[MikeM173]

What was it you were looking for from a turbo? Why do you need spool up so low? What are you planning on using the car for? Most people don't set their car up for what it is they want to use it for. They just buy a turbo everyone else says they are happy with (those people don't know how to set up either) or they buy a turbo based on horsepower numbers. No offense but this is the wrong approach. You'll never be fully happy that route. Also spool up time is based on the tune as well. If your turbo is the turbo you need for the application you want but you aren't hitting the right marks then revisit the tune. If your stuck on the tune then post your tune up and ask for help. Otherwise the answers are in the setup.

[JimmyS]

If you have some logs of your K04 setup, out of curiousity, how much air were you flowing then vs. the 6758 at the same rpms? I base my improvements on time vs. speed so I'll know if I've done any good when I'm working on my tune.

I remember going through a number of GMTech's posts on different forums when he installed the 6758 and he was flowing more air at 4500rpm's than the K04 could flow at any rpm and if I remember correctly, he mentioned that the 6758 was spooling roughly 500rpms later than the K04 which isn't bad considering how much more air it flows.

[MikeM173]

Airflow numbers are inaccurate to base improvements on.

[cobaltssoverbooster]

i used to track boost build by log time stamp and recorded rpm

[JimmyS]

But time versus speed aren't.

[hhrfreek]

I guess when I look at a turbo and see claims it spools similar to stock and holds boost through redline, I expect it to be a bit more responsive down low and faster spool between shifts. Is this turbo what I want? Probably. I drive spirited and track it a few times a year. The car is absolutely faster. On 24psi max with both turbos...I roll 60-100 in 3.6s on 6758. On the k04 I was 60-95 in 4s so I imagine around 4.7ish, but I didn't rev over 6800 without stiffer valve springs. I do have a 3.91 diff though now vs 3.73 on stock...not sure how much that effects the current time.

Jimmy are you on stock block?...finding out many people are going well beyond 24psi on stock block.

[JimmyS]

Yes stock block - upgraded valve springs are the only internal engine upgrades I have. As for spooling between shifts my auto tranny setup tuned with 2.25 Beta keeps boost pretty close to a flat line between shifts. Sounds like you've got a decent tune there. Didn't you have an HHR running in the low 12's?

[cobaltssoverbooster]

Boost tests in 3rd gear and disregard speed due to wheel spin. I did verify when wheel speed initiated; also an indicator of faster spool. There are many ways to track spool build. I also did 2k rpm digs and 2500 digs to verify global decrease in spool time.

Tracking is very much so tuner preference and if your also the driver tailor tests to how it will be driven.

I'm sure I sound like I'm repeating myself, sorry if it's annoying.

[hhrfreek]

Yes stock block - upgraded valve springs are the only internal engine upgrades I have. As for spooling between shifts my auto tranny setup tuned with 2.25 Beta keeps boost pretty close to a flat line between shifts. Sounds like you've got a decent tune there. Didn't you have an HHR running in the low 12's?

Thats why I want an auto. I granny shift and that is another reason I notice the spool. I NLS this car until I started running e47 on the stock turbo but the clutch gave up once so I haven't tried again in a year. The HHR was a SC2.4l. I would guess mid-high 13s on street tires. I never got back to the track at 300whp. I got out of it and into the Solstice. I pulled the motor thinking I'd get a base, but I got a GXP instead and parted out that engine to buy a daily so I could mod at my leisure.

Boost tests in 3rd gear and disregard speed due to wheel spin. I did verify when wheel speed initiated; also an indicator of faster spool. There are many ways to track spool build. I also did 2k rpm digs and 2500 digs to verify global decrease in spool time.

Tracking is very much so tuner preference and if your also the driver tailor tests to how it will be driven.

I'm sure I sound like I'm repeating myself, sorry if it's annoying.

No not at all. I just wanted to make sure there wasn't a different way of logging it from a low rpm pull and I guess in comparison to other 6758 setups is that about right? I think my expectations were just different. This is my first turbo swap. When I first put the ZFR on I didn't see 24psi until about 4200 with stock PID tables. I figured them out to get down to 3900, but that seems about it.

[cobaltssoverbooster]

I think your going about it the right way.
Being that this turbo is a larger frame size I would be happy to only have the spool time off by 600 rpm. That would put you ~3800 so your doing very well in my book. Tune fines may lower you spool even more so keep trying stuff out when you have time.

[MikeM173]

Why do you need such a low spool time on a larger turbo? This is why people break transmissions. They don't mod for the car and their plans. When you shift out of a WOT into the next gear what are your rpms? I can tell you if you shift around 7000rpm they will be around 3900 if I remember correctly. Why do you need a spool lower then that? A highway pull? If you shift into the correct gears at the correct speeds then that is not an issue either. Coming out of a corner I can see wanting a quicker spool but it is strictly for that moment unless you are tracking her in which case you set the car up for it. I'm not trying to repeat myself but for the most part most people do not need as low of a spool like they think they do. Not saying you don't I'm just saying most people are after arbitrary things that have no meaning for what they are using the care for when they could just learn to drive. Again not accusing you of any of this so please don't take offense.

[cobaltssoverbooster]

that is true...its very common for high loads in a low rpm range to help the input shaft escape from the transmission case.

[mkriebs]

I have never understood the premise that a larger turbo will spool like the KO4 which is tiny. Like Mike said, your spool is going to be based on what you need the car to do, most of the time, spooling before 3900 is only used when taking off, and even then, a later spool would be beneficial in keeping parts in the car.

I think as a community of enthusiasts we get too caught up in the "he said it does this" and we think objectively about things instead of subjectively. Objective thinking is giving ourselves goals: power numbers, lbs of boost, 40-100 times, etc that we feel we should meet, when there are extraneous conditions that manipulate every end goal. Instead, we should be thinking subjectively: what am I doing with the car, where should my powerband be, what parts do I need to make this happen.

Beyond that, I think you are getting close to the full potential of spool out of the 6758. It is quite a bit larger of a turbo and no matter the technology applied to new turbos, they will never defy physics. Physics means that larger is naturally going to spool later. But this isn't a bad thing, you just have to learn to tailor your driving to this new turbo.

[hhrfreek]

This is my first experience swapping a turbo, if it hadn't been I'm sure I wouldn't be posing the newb question. You guys brought up good points. I think my expectations were just too high. From all that is said about EFR turbos I thought they were the holy grail. So I came into this thinking the spool would be just as low and fast as the K04, and keep up to 7500rpms...but that ain't happening as I found out. Kind of chuckling at myself actually. Depending on gear I am much higher around 46-4800rpm when shifting at 7-7200rpms. My goal with this setup was to be under 4s 60-100 and at 3.6, the car is a little faster than I thought it would be on 24psi. I want to get more into drag racing and have a responsive street car, so this should fit well into my plans as there is a lot more power available with this turbo and I am exploring the possibility of swapping in an auto.

[MikeM173]

A lot can affect turbo spool. Timing, PID tables, all of the torque management stuff, wastegate table, etc. You need to understand how to tune for spool time though. Also keep in mind that changing how quickly she spools does not change where she spools at but rather gets you to that point quicker. The car will only full spool by a certain rpm. After that you need to figure out how to make it spool quicker to that point. Hopefully that made sense.

[2000Firehawk]

Yes stock block - upgraded valve springs are the only internal engine upgrades I have. As for spooling between shifts my auto tranny setup tuned with 2.25 Beta keeps boost pretty close to a flat line between shifts. Sounds like you've got a decent tune there. Didn't you have an HHR running in the low 12's?

I have the HHR SS automatic, that ran 12.3s all day, my last time at the track, with a best of 12.30

[JimmyS]

Sweet!

[mkriebs]

A lot can affect turbo spool. Timing, PID tables, all of the torque management stuff, wastegate table, etc. You need to understand how to tune for spool time though. Also keep in mind that changing how quickly she spools does not change where she spools at but rather gets you to that point quicker. The car will only full spool by a certain rpm. After that you need to figure out how to make it spool quicker to that point. Hopefully that made sense.

And this is something I will be working on getting a grasp on soon. Seems like there are a million factors in the E69 that affect this. Should be a good learning experience.