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Swapped superchargers from a D1SC to a D1X. I wanted a quiet drive and wanted to put a little more into the car. Ran a couple logs and built what the two different boost curves look like.
D1X setup is with a 4" inlet. D1SC is with a 3.75" inlet. So, not 100% apples-to-apples comparison, but pretty close. If anything it would have made the D1SC more pronounced. Combination is a custom Procharger installation on a 383 all-bore engine with a large front mount (1,500 CFM). Setup makes ~700 HP D1SC and ~800 HP D1x. Boost curves are ambient/pressure corrected to 1.013 bara and a 75 deg F day (former gas turbine engineer, so the correction is actually done right). So, that part is apples-to-apples.
Inlet air temperature rise for the D1SC dT is ~35 deg F and D1X dT is ~25 deg F. So, the D1x does show up as a much more efficient (cooler) blower. From the below curves it can clearly be seen that the D1SC is a much stronger low-load performance blower, while the D1X is more of a 'peaky' blower. The car does feel a little softer down low, but it continues to pull up top where it nosed over with the D1SC - which is exactly what the curves show.
So, in summary - if you want area under the curve and don't care about a peak number, go D1SC. If you want that peak number or do all your business at 5,500+ rpm, go D1X.
Great data.
Would adding a wastegate to your setup to bring in boost faster with a smaller pulley but still bleed it off up top to maintain your current boost peak?
Both blowers are belted to 62k rpm. So, can't really go up from there.
I never really liked the waste-gate idea also. You can make it work, but unless you are crazy high compression, hitting the motor with more boost than you want for the last 500 rpm and just dropping the timing down works fine.
Great data.
Would adding a wastegate to your setup to bring in boost faster with a smaller pulley but still bleed it off up top to maintain your current boost peak?
I did something like with my BoV.
I upgraded from a Si to a Ti with a billet impeller and wanted to limit the WHP by limiting the max boost. I T'd off the manifold pressure reference line to a manual Boost Controller and left the outlet side open.
I used a pressure gauge to set the Boost Controller to ~ 10 PSI. Combined with the spring on the BoV it was making ~ 12 PSI and 747 WHP.
Both blowers are belted to 62k rpm. So, can't really go up from there.
I never really liked the waste-gate idea also. You can make it work, but unless you are crazy high compression, hitting the motor with more boost than you want for the last 500 rpm and just dropping the timing down works fine.
Why would there be a problem with using a waste gate or BoV to limit boost?
Using a bigger CSC and/or a smaller pulley brings in the boost earlier.
The waste gate idea on a centri is a terrible idea. Why limit peak boost? You are going to continue to build heat spinning the blower that fast just to send the air to the atmosphere. If you want more boost down low without building more up top as well you got the wrong blower and should of went with a roots.
The D1x will keep making more boost above its max recommended impeller speed of 62,000. I spin mine to ~66,000 and it keeps gaining boost the whole way.
The waste gate idea on a centri is a terrible idea. Why limit peak boost? You are going to continue to build heat spinning the blower that fast just to send the air to the atmosphere. If you want more boost down low without building more up top as well you got the wrong blower and should of went with a roots.
The D1x will keep making more boost above its max recommended impeller speed of 62,000. I spin mine to ~66,000 and it keeps gaining boost the whole way.
Not second guessing you at all as I've only read about it and just for my own curiosity but has that been the real world experience from people who have tried it?
I read about it a while ago but it doesn't seem like anyone is really doing it and probably for the reasons you're stating.
It sounded like a good idea but I can very easily see heat becoming an issue on an actual pull and not just on a dyno.
Why would there be a problem with using a waste gate or BoV to limit boost?
Using a bigger CSC and/or a smaller pulley brings in the boost earlier.
I didn't say there would be a problem, I said I didn't care for it. If you want to restrict the blower, do it on the inlet - you don't take the parasitic loss, the additional heat, and you get the exact same effect. And it takes 20 min to make an aluminum orifice.
Not second guessing you at all as I've only read about it and just for my own curiosity but has that been the real world experience from people who have tried it?
I read about it a while ago but it doesn't seem like anyone is really doing it and probably for the reasons you're stating.
It sounded like a good idea but I can very easily see heat becoming an issue on an actual pull and not just on a dyno.
You don't see anyone doing it because it's a terrible idea. The people that actually tried it aren't likely doing it anymore because it didn't work as expected.
Swapped superchargers from a D1SC to a D1X. I wanted a quiet drive and wanted to put a little more into the car. Ran a couple logs and built what the two different boost curves look like.
D1X setup is with a 4" inlet. D1SC is with a 3.75" inlet. So, not 100% apples-to-apples comparison, but pretty close. If anything it would have made the D1SC more pronounced. Combination is a custom Procharger installation on a 383 all-bore engine with a large front mount (1,500 CFM). Setup makes ~700 HP D1SC and ~800 HP D1x. Boost curves are ambient/pressure corrected to 1.013 bara and a 75 deg F day (former gas turbine engineer, so the correction is actually done right). So, that part is apples-to-apples.
Inlet air temperature rise for the D1SC dT is ~35 deg F and D1X dT is ~25 deg F. So, the D1x does show up as a much more efficient (cooler) blower. From the below curves it can clearly be seen that the D1SC is a much stronger low-load performance blower, while the D1X is more of a 'peaky' blower. The car does feel a little softer down low, but it continues to pull up top where it nosed over with the D1SC - which is exactly what the curves show.
So, in summary - if you want area under the curve and don't care about a peak number, go D1SC. If you want that peak number or do all your business at 5,500+ rpm, go D1X.
What were the pulley sizes (crank and blower) in both setups?
Really quick also, when you say an all bore 383, what does that consist of as far as block and rotating assembly?
I'm imagining a big bore short stroke combo and the way that power curve looks for the D1X, I'd expect the shift point to be somewhere north of 7K rpm.
Really quick also, when you say an all bore 383, what does that consist of as far as block and rotating assembly?
I'm imagining a big bore short stroke combo and the way that power curve looks for the D1X, I'd expect the shift point to be somewhere north of 7K rpm.
4.100 bore dry-sleeve sleeved block, stock stroke. Stock hardened crank (LS1), stock rod (LS1) modified with a bronze bush. Low compression, 8.2 and high boost. I run a small cam 222/230 to keep the rpm down and make it drive nice. I wanted the better rod to stroke ratio, and I keep the cam small to cap the peak rpm sub-7000 rpm.
People always gravitate to the stock rod, but this build has been making 700-800+ HP for 18 years now (literally), and 50,000+ miles with multiple races/track days/etc.... The only problems I have had are minor bits, and I recently had a head issue where a couple of the ARPs had loosened up.
The motor is starting to show slightly lower oil pressure at hot-hot idle, so I suspect I'll have to do something about it in the next couple years, but at this point, this motor has had a long/hard life and it doesn't owe me anything.
ATI superdamper to 7" aluminum drive pully. 3.1" Reichard Racing supercharger pulley. SDCE tensioner system. Car spins up to 6,700 rpm.
So, spinning each blower to 62,029 rpm if you do the math.
Thats as apple to apple as it gets right there. You often see these blower comparisons or same blower different cam or head comparisons and they use a different blower pulley combo to get boost to equal. Same pulley combo is what I like to see on these type of comparisons.
Well done!!!
I’m surprised you don’t see belt slip with the 3.1. I use an 8.25 and 3.55 pulley combo shifting about 7000 rpm currently on the D1x. No slip and they are standard Procharger pulleys.
Thats as apple to apple as it gets right there. You often see these blower comparisons or same blower different cam or head comparisons and they use a different blower pulley combo to get boost to equal. Same pulley combo is what I like to see on these type of comparisons.
Well done!!!
I’m surprised you don’t see belt slip with the 3.1. I use an 8.25 and 3.55 pulley combo shifting about 7000 rpm currently on the D1x. No slip and they are standard Procharger pulleys.
You can't get Reichard's anymore, but they are a pretty aggressive pulley. They do a pretty good job not slipping at the smaller sizes - but they also break belts if everything isn't perfect.
4.100 bore dry-sleeve sleeved block, stock stroke. Stock hardened crank (LS1), stock rod (LS1) modified with a bronze bush. Low compression, 8.2 and high boost. I run a small cam 222/230 to keep the rpm down and make it drive nice. I wanted the better rod to stroke ratio, and I keep the cam small to cap the peak rpm sub-7000 rpm.
People always gravitate to the stock rod, but this build has been making 700-800+ HP for 18 years now (literally), and 50,000+ miles with multiple races/track days/etc.... The only problems I have had are minor bits, and I recently had a head issue where a couple of the ARPs had loosened up.
The motor is starting to show slightly lower oil pressure at hot-hot idle, so I suspect I'll have to do something about it in the next couple years, but at this point, this motor has had a long/hard life and it doesn't owe me anything.
That's an interesting combo, sounds like for the refresh adding a set of nice rods and slightly more aggressive cam would provide breathing room for moving those shifts into the 7,500+rpm plus range which seems like where the blower wants to go.
I already have a tough time hooking at lower speeds, a PD would only make that worse.
A CSC will never have extra power or much of any power down low. Using a smaller pulley will bring the CSC in sooner as in mid band, about where you are getting good hook.
I want more boost sooner (mid band) but to not go over 750 WHP.
Why does no one use this? Other than me, who wants to throw away power? LOL
I have never liked the idea of a restrictor plate. That is a guaranteed way to create more heat. The air pulled into the CSC is thinner (lower pressure) so it takes more compressing to get the the same level boost. If I remember correctly A&A advises against using a restrictor plate for this reason.
And I do have a **** if I ever want to go for more.
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D1SC vs. D1X (some actual data) 
