Powerdyne BD-11a versus Powerdyne XB-1A dyno numbers - need some input

[MuscleJunkie]

Ok, I have an update and a couple conclusions. Also curious to hear any addition input/thoughts about it

As I previously posted, we made some effort to address potential belt slip I was experiencing with my 2.7/6.5 pulley combo (The Powerdyne XB-1a has a 3.44 gearbox ratio). It seems that this effort paid off and we saw some big torque increases through the rpm range. FYI, it’s estimated the 2000 Explorer with 302 5.0 Liter Windsor V8 has a driveline loss of 25% or more because of the 4R70W automatic transmission and Borg Warner 4405 AWD system. Add this to these numbers if you want to know the crank hp/torque numbers.

It also appears that the tune needs to be adjusted because it appears to sharply pull engine timing (???) at 4500rpm. My understanding is since we are making more power/boost due to reduced belt slip (??) the previous very safe tune can be adjusted and we will ultimately see these new gains continue up through past 4500 rpm instead of the current drop due to pulled timing. Shop estimates an additional gain of perhaps 25 hp or more after 4500

Here are two Dyno sheets

The 1st shows a comparison between last high Dyno run on October 9 before fixing the belt slip problem (ORANGE) and October 30 (GREEN) after the effort to fix it. You can see the gains in the lower and mid rpm range

There was some question about how much boost is being lost by the WTA intercooler. The second Dyno sheets show the last two runs on October 30. If you see the bottom graph on that sheet, you can see the pre-intercooler boost pressure (GREEN) and post-intercooler (RED).

We are only seeing a peak of 0.11lbs of boost loss due to the intercooler.

So some conclusions and next steps??

* It appears we had some success in reducing belt slip with the 2.7/6.5 pulley combo

* Previous very safe tune needs to be adjusted as it seems to be pulling timing at around 4500 rpm

* Need to find a way to install a bigger crank pulley The current 2.7/6.5 pulley is now only spinning the blower in to 40k rpm range. I’m told this blower is “pesky” and sees bigger gains at higher rpm’s when compared to the BD-11a. Right now the water pump pulley on the Explorer prevents me from installing a bigger supercharger crankshaft pulley (see last photo). I am no longer driving a fan off the water pump since going to an efan solution. The Explorer 302 uses a much shorter front dress(???) that the Mustang 302 so I might need to find a custom solution to solve this issue. A bigger crank pulley will allow me to spin the blower faster with reduced chances of belt slip which should result in even more HP and torque gains on this combo.

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[Blown]

Bam! Awesome and you'll get more above 4,500rpm with tweaks to the tune.

That is a beautifully flat torque curve and starting with 350ftlbs at 3,000rpm!!! That will get you moving!

I see the boost coming in at 2,700, climbing all the way to 5,700rpm and then flattens! That tells me you got room above 4,500 for more power! I can see cutting timing above 4,500 as the boost is getting up there high enough to be needed to prevent predetonation. One degree of timing is 2-3 horses while 1lb of boost is 15-19hp. My only concern would be exhaust size as you push it further.

Perhaps a Machine Shop can make you some custom pulleys??? I'd try a smaller blower pulley before I went custom.

 

[MuscleJunkie]

Bam! Awesome and you'll get more above 4,500rpm with tweaks to the tune.

That is a beautifully flat torque curve and starting with 350ftlbs at 3,000rpm!!! That will get you moving!

I see the boost coming in at 2,700, climbing all the way to 5,700rpm and then flattens! That tells me you got room above 4,500 for more power! I can see cutting timing above 4,500 as the boost is getting up there high enough to be needed to prevent predetonation. One degree of timing is 2-3 horses while 1lb of boost is 15-19hp. My only concern would be exhaust size as you push it further.

Perhaps a Machine Shop can make you some custom pulleys??? I'd try a smaller blower pulley before I went custom.

I’m trying to understand more about the tune. If you look at the run before the belt slip issue is addressed you’ll see the horsepower continue to climb after 4500 rpm. The tune hasn’t changed so I’m guessing since we have less belt slip means that there is more boost after 4500 RPM, and since the tune is a so-called very safe tune until we worked out these issues that is why the timing is being pulled out?

My exhaust is 2.5 from the collectors (with absolutely no restrictions) then X-pipe then into two separate Saleen Borla mufflers and resonator and out true dual 2.25 on each side. Looking at flow number calculations, I’m thinking this should be enough exhaust??

I’m already running a 2.7 supercharger pulley and worried if I go smaller it would just give me more belt slip. ASP said they can make me a bigger, crank pulley. I just need to find out if there’s an option to make the pulley for the water pump smaller to be able to provide clearance for the larger crank pulley.

 

[Blown]

I’m trying to understand more about the tune. If you look at the run before the belt slip issue is addressed you’ll see the horsepower continue to climb after 4500 rpm. The tune hasn’t changed so I’m guessing since we have less belt slip means that there is more boost after 4500 RPM, and since the tune is a so-called very safe tune until we worked out these issues that is why the timing is being pulled out?

My exhaust is 2.5 from the collectors (with absolutely no restrictions) then X-pipe then into two separate Saleen Borla mufflers and resonator and out true dual 2.5 in each side. Looking at flow number calculations, I’m thinking this should be enough exhaust??

I’m already running a 2.7 supercharger pulley and worried if I go smaller it would just give me more belt slip. ASP said they can make me a bigger, crank pulley. I just need to find out if there’s an option to make the pulley for the water pump smaller to be able to provide clearance for the larger crank pulley.

Yes, Timing is pulled to run it safer until you all figure out issues, boost amount and air fuel ratios etc etc.

My bad, That will do it! I got exhaust envy, may I borrow your set-up?

You can spin the coolant pump faster but only to some limit without issue. It may be that an aftermarket pump with different impeller would work better at higher rpm.

 

[Josh P]

Without the mechanical fan, you could run an electric water pump.

 

[MuscleJunkie]

Without the mechanical fan, you could run an electric water pump.

Any idea how far the motors of those electrical pump stick out - wondering if it would allow me enough clearance. Are the electric pumps reliable?

 

[Josh P]

Any idea how far the motors of those electrical pump stick out - wondering if it would allow me enough clearance. Are the electric pumps reliable?

I'd trust the electric motor as much as the serpentine belt. You can get a few different styles, one that goes where the current pump is, or an inline you put on the radiator hose.

 

[Blown]

You would likely plate-off the mechanical pump with a smaller idler pulley bolted into the plate to replace the pump pulley and then run an electric inline pump somehow.

 

[CDW6212R]

...

* Need to find a way to install a bigger crank pulley The current 2.7/6.5 pulley is now only spinning the blower in to 40k rpm range. I’m told this blower is “pesky” and sees bigger gains at higher rpm’s when compared to the BD-11a. Right now the water pump pulley on the Explorer prevents me from installing a bigger supercharger crankshaft pulley (see last photo).

...

View attachment 446836

By this picture you have plenty of room for a 7" crank pulley. The distance between the WP and blower pulley is just half of the diameter you may gain. So if the gap is 1/2", then you could make the pulley one inch larger.

But I'm not sure you want to go far beyond 7", the mounting method may or may not be stable enough with a much larger pulley. I'd ask your shop expert, what he thinks of the strength of that crank pulley attachment. If he seems confident in it, then you could push the size so it's say an 1/8" from the WP pulley. Note it could be interesting to change the main belt if needed.

I like that power curve a lot, that's great for a 6psi boost level so far.

 

[MuscleJunkie]

...


By this picture you have plenty of room for a 7" crank pulley. The distance between the WP and blower pulley is just half of the diameter you may gain. So if the gap is 1/2", then you could make the pulley one inch larger.

But I'm not sure you want to go far beyond 7", the mounting method may or may not be stable enough with a much larger pulley. I'd ask your shop expert, what he thinks of the strength of that crank pulley attachment. If he seems confident in it, then you could push the size so it's say an 1/8" from the WP pulley. Note it could be interesting to change the main belt if needed.

I like that power curve a lot, that's great for a 6psi boost level so far.

Impeller calculations

At 5500 rpm

2.7/6.5 - 45548.15 rpm

2.7/7.0 - 49051.85 rpm

2.7/8.0 - 56059.26 rpm

I believe the XB-1a Si like the Vortech V1 SI has ABEC 7 bearings rated for 56 to 62k. Powerdyne producer recommends 50k for longevity. I know of one guy on YouTube that was spinning this build of blower with YSI trim in the mid 60k to 70k range

 

[CDW6212R]

If your trusted man there convinces you that the crank can be bigger, what will it get you if you made it close to 7.5" big? What blower pulley could you use to hit the 50k blower speed?

My Kenne Bell is a 18k rated thing, they say to now go over that. I'm king of aiming for the 13k or so range, which will be a little over a 2:1 ratio. I know a man who races one that pushes his 2.8 to near 20k always in his 1/4 mile Saleen Mustang. I think you'd be like me Jim, build it to likely survive 100k miles, or maybe 200k.

If you can fit a 7.5" crank pulley, then a 3" blower pulley will net you just over 50k of the blower, at your current rpm. If you rebuild the engine, then you can alter the rpm range and gain a ton more. I'm doing a stock 302 baseline build, hit 10psi and stock 5k rpm, then later do a 337 engine to push to at least 6k rpm, and near 15psi. How patient are you, I know you are, can you be satisfied with the current level for a while?

 

[MuscleJunkie]

If your trusted man there convinces you that the crank can be bigger, what will it get you if you made it close to 7.5" big? What blower pulley could you use to hit the 50k blower speed?

My Kenne Bell is a 18k rated thing, they say to now go over that. I'm king of aiming for the 13k or so range, which will be a little over a 2:1 ratio. I know a man who races one that pushes his 2.8 to near 20k always in his 1/4 mile Saleen Mustang. I think you'd be like me Jim, build it to likely survive 100k miles, or maybe 200k.

If you can fit a 7.5" crank pulley, then a 3" blower pulley will net you just over 50k of the blower, at your current rpm. If you rebuild the engine, then you can alter the rpm range and gain a ton more. I'm doing a stock 302 baseline build, hit 10psi and stock 5k rpm, then later do a 337 engine to push to at least 6k rpm, and near 15psi. How patient are you, I know you are, can you be satisfied with the current level for a while?

I’m thinking a 7.5 or even 8 would be better. 8 would definitely allow me to run a larger SC pulley and reduce chances of further belt slip.

At 5000 rpm

2.7/8.0 - 50962 rpm
2.8/8.0 - 49142 rpm
3.1/8.0 - 44387 rpm

At 50k or more is possibly where this blower really starts pushing all those 1200cfm. That’s my guess

I’m patient - haven’t driven the truck in about a year because all of this. I want to get the tune sorted out and enjoy what it has for the time being while working on the next steps.

You’re right I want this thing to be durable and have a great longevity. The biggest thing is that I got away from the belt driven blower to this gear driven blower. Hopefully it’s built strong and is able to deliver on some good reliable power.

 

[CDW6212R]

It looks like a nice promising power curve now, and with a little more engine, and rpm, it should be really strong. I think I'd first consider the next step of the engine , specifically the shift point. You can balance the reliability of the supercharger against the engine, how long you expect each to live. If you worry more about the engine, push the blower rpm, if the other way, lower the blower rpm and rely on the engine more. I think a SBF can easily live at 6k for ages, 20 years, with the right valvetrain and camshaft. That 6k is not very high, it is for the stock parts, but not for countless that have been built forever. Note the shift going up will impact the trans and tires, traction etc. Do you worry about that much or how the power gets there? I've wondered all of that and hope that the drive shafts and AWD will be okay. If you feel comfortable in all of it, push the next engine and plan the crank pulley size for that shift rpm.

If you shift the upgrade engine at 6k, then the blower rpm will go up 20%. So keeping the 6.5 crank pulley would require a blower pulley bigger than 3", about 3.3" to hit 50k. That's worth considering before jumping the crank pulley up too much. The stock 302 is good enough to make 400 flywheel horsepower, but it's pushing the pistons a lot there too. I'm going to be easy with my first 302 to save it; low mileage, to sell it afterwords.

 

[MuscleJunkie]

It looks like a nice promising power curve now, and with a little more engine, and rpm, it should be really strong. I think I'd first consider the next step of the engine , specifically the shift point. You can balance the reliability of the supercharger against the engine, how long you expect each to live. If you worry more about the engine, push the blower rpm, if the other way, lower the blower rpm and rely on the engine more. I think a SBF can easily live at 6k for ages, 20 years, with the right valvetrain and camshaft. That 6k is not very high, it is for the stock parts, but not for countless that have been built forever. Note the shift going up will impact the trans and tires, traction etc. Do you worry about that much or how the power gets there? I've wondered all of that and hope that the drive shafts and AWD will be okay. If you feel comfortable in all of it, push the next engine and plan the crank pulley size for that shift rpm.

If you shift the upgrade engine at 6k, then the blower rpm will go up 20%. So keeping the 6.5 crank pulley would require a blower pulley bigger than 3", about 3.3" to hit 50k. That's worth considering before jumping the crank pulley up too much. The stock 302 is good enough to make 400 flywheel horsepower, but it's pushing the pistons a lot there too. I'm going to be easy with my first 302 to save it; low mileage, to sell it afterwords.

Don, what issues might be caused by increasing the crank pulley size from 6.5 to say 7.5 or 8??

 

[CDW6212R]

That pulley is bolted onto the balancer at the three threaded pulling holes right? I don't know how true every balancer is so the new pulley is flush and runs true to the main pulley. You obviously did a great job to mount that one and it spins true. That was my only concern, so I suggested leaving that choice up to your mechanic.

Seeing your rpm figures now with the 6.5" pulley and the stock engine 5k rpm shifting, that begs the question of a next step/engine. Will the next engine run 6k, 20% more, and thus the 50,000 blower rpm might end up being 60,000? You control all of that with the choices of shift point, both pulley sizes, and how the next engine is built.


I've considered my plans, two engine steps, for many years. I like the first baseline being mild to sort out all of the operating system details, the exhaust and supercharger possibilities. Then the new engine I can aim to be very reliable and still hit my modest goals. You are almost done with your first main step, now you are contemplating the next and final details, choices etc. You might be done way before I get my baseline engine in and running. Keep going.

 

[Blown]

That pulley is bolted onto the balancer at the three threaded pulling holes right? I don't know how true every balancer is so the new pulley is flush and runs true to the main pulley. You obviously did a great job to mount that one and it spins true. That was my only concern, so I suggested leaving that choice up to your mechanic.

Seeing your rpm figures now with the 6.5" pulley and the stock engine 5k rpm shifting, that begs the question of a next step/engine. Will the next engine run 6k, 20% more, and thus the 50,000 blower rpm might end up being 60,000? You control all of that with the choices of shift point, both pulley sizes, and how the next engine is built.


I've considered my plans, two engine steps, for many years. I like the first baseline being mild to sort out all of the operating system details, the exhaust and supercharger possibilities. Then the new engine I can aim to be very reliable and still hit my modest goals. You are almost done with your first main step, now you are contemplating the next and final details, choices etc. You might be done way before I get my baseline engine in and running. Keep going.

It's four bolts on these Explorer combo crank pulley/balancers.................................very stout! I had the mating surface of the crank/balancer machined a bit, nice and flat to make a nice mounting surface for the blower pulley.

A custom. larger crank pulley shouldn't be a problem if it clears and isn't stupid out of balance or wonky.

I got no belt slippage that I can hear with 3" pulley this evening, looking like 8lbs.

 

[MuscleJunkie]

The Powerdyne pulley I have is two piece. There is a billet spacer that fits inside the original balancer, and then the outer pulley bolts through/onto that. It uses three bolts…. Last photo shows some of the original BD-11a Explorer kit with the pulley that bolts to balancer

 

[Blown]

I assumed they bolted through using the 4 existing holes like I set mine up.

 

[CDW6212R]

That was the choice Powerdyne made to attach their pulley. As long as the pulley spins perfectly straight then it'll be fine. I also would have considered machining the front of the balancer, not being sure how straight the OEM front surface is on each balancer. Whatever does work is fine.

 

[MuscleJunkie]

A few pics. 1st the original stock balancer which was shot then the new one which we machined for the billet spacer. All were three hole. Are some Explorers 4 hole??