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When I put together my current combo...Ls3 block with forged rods/pistons, custom Cam Motion 232/248 duration cam, stock 241 heads, ls6 intake, and stock throttle body my plan was to upgrade the top end next winter.
Im currently spinning the D1x to 60,000 rpm making 14 psi which is down about a pound and a half now that summer is here. I’m very impressed with this little blower, but now I want more.
Looking at prices im having second thoughts about upgrading the top end. An F1a-94 is an easy drop in upgrade and will do more for me than a new top end so now I’m leaning toward that option.
Below is a screen shot from my last log log of a wot 2nd gear pull right at the peak rpm of the 2-3 shift. Temp was about 80 degrees.
I would go head unit personally. Power gained from a bigger top end can be offset with a pound or two of boost rather easily.
Ya it kind of seems like a no brainer considering I'm not seeing any iat or ect issues that would suggest excessive restriction. Also considering the head unit is a few bolts and a clamp to change it and I can sell my current D1x head unit pretty easy.
I guess if the bigger head unit causes any issues with this restrictive top end I'll just have an excuse to work on the car some more...LOL
What's max impellar speed? What are the goals? Seems like decent heads will make more power at less boost letting you pulley down again without swapping to a larger blower.
What's max impellar speed? What are the goals? Seems like decent heads will make more power at less boost letting you pulley down again without swapping to a larger blower.
The D1x is rated at 1075 horse power with a recommended max impeller speed of 62,000. Currently with an 8.25 lower and 3.9 upper I'm spinning it to about 60,000. Initial plan is to get bigger injectors and a 3.7 pulley to max it out. Knowing myself that will be fun for a little bit before I want more.
More power NA more power in boost. A head swap should be worth 50+rwhp and drop boost. Pulley down and pick up another few psi maxing out the blower and you'll pick up over 100whp. The F1A94 can support more power but you'll still be driving it with the same motor that can only flow so much.
More power NA more power in boost. A head swap should be worth 50+rwhp and drop boost. Pulley down and pick up another few psi maxing out the blower and you'll pick up over 100whp. The F1A94 can support more power but you'll still be driving it with the same motor that can only flow so much.
Hmm...now the question is with my low iat's at 60,000 impeller speed is the blower really done at 62,000 rpm?
Hmm...now the question is with my low iat's at 60,000 impeller speed is the blower really done at 62,000 rpm?
I always thought max impeller speed was a recommended mechanical limit that if you went over they wouldn't warranty the blower. It wasn't related to IATs. Never really investigated though.
I always thought max impeller speed was a recommended mechanical limit that if you went over they wouldn't warranty the blower. It wasn't related to IATs. Never really investigated though.
Basically what I meant was can the blower continue to make more boost above 62,000 rpm without a crazy impact on iat's. I'm sure plenty of people have spun the blowers over max recommended rpm.
Basically what I meant was can the blower continue to make more boost above 62,000 rpm without a crazy impact on iat's. I'm sure plenty of people have spun the blowers over max recommended rpm.
Ah I gotcha. I wouldnt be surprised if you lost 2 psi with good ported heads. Pulley down and add that boost back and it's sure to pick up some good power.
Simple/cheaper approach - head unit. Down the road - you could add top end (thicker deck/more stable) with 1/2" studs and really push it.
I think this is the route I'm going to take. Hopefully run the car at the track as it is now once then get bigger injectors and max out the D1x. Then go with the F1a-94 and start easing it up a pound or so at a time with that. Currently I have the untouched 241's with ls9 gaskets and arp studs which will hopefully be good to 20 psi.
What kind of power is that setup making? My sbe ls3 with the D1X put out an easy 980rwhp with 224/239 cam on e85. That was at 21psi with a 8.190/3.85 combo. Still had room for a 3.7 pulley. The X has made over 1000 wheel so I would work on a better top end.
What kind of power is that setup making? My sbe ls3 with the D1X put out an easy 980rwhp with 224/239 cam on e85. That was at 21psi with a 8.190/3.85 combo. Still had room for a 3.7 pulley. The X has made over 1000 wheel so I would work on a better top end.
I haven't had it on a dyno so I have no real idea what it's making. The local track is having a street car race this Friday so I'll have a better idea once I run the car. Weather man is calling for storms though. Cam is 232/248 custom centri cam from Cam Motion. I've been running E50 with 17 degrees peak timing dropping down to 15 over 6800 for the shift. Car has a built 4l60E in it...LOL. My intake might be limiting it a bit as well which may explain why I'm seeing less psi than you even with a more restrictive top end. My cam is significantly larger though also. It seems significantly more powerful that the 650 rwhp I had on sbe ls1 so it may very well be making 750-800 rwhp now I just can't say for sure. Pulls clean all the way to shift point through 2nd and 3rd gear at wot. No signs of belt slip as boost climbs all the way and no belt dust or anything.
Here is a picture of the engine bay that shows the GTO procharger intake tube (possible restriction) even though I have a blower guard on it instead of a filter.
My vote is for a better top end. It would make a new head unit down the road shine even more. The heads/intake will flow only so much so even if you put a -94 on it, you will still need to upgrade heads/intake. More NA hp (esp on a blower) the more power the combo will make. The D1X is an awesome street blower that has made over 1000whp on a few cars and has been in the 4s on 235 tires on a 3200 lb car.
You have a couple options that aren’t that bad. Could swap to LS3 top end with a new cam or a set of TFS as cast heads (cathedral) with a BTR intake/holley style intakes or even the LS6 If on a low budget.
My vote is for a better top end. It would make a new head unit down the road shine even more. The heads/intake will flow only so much so even if you put a -94 on it, you will still need to upgrade heads/intake. More NA hp (esp on a blower) the more power the combo will make. The D1X is an awesome street blower that has made over 1000whp on a few cars and has been in the 4s on 235 tires on a 3200 lb car.
You have a couple options that aren’t that bad. Could swap to LS3 top end with a new cam or a set of TFS as cast heads (cathedral) with a BTR intake/holley style intakes or even the LS6 If on a low budget.
If I went with heads I'd probably go with an aftermarket casting cathedral head. I currently have an ls6 intake. I really need to get this thing on a dyno before I make a decision not only to see what it's actually making, but also to measure gains going forward.
My previous sbe ls1 with 228r cam and the same top end blower combo making 14 psi with a 7.65 lower and 3.9 upper pulley felt strong in the midrange up to 6200 rpm. This new combo by seat of the pants kills that old combo every where, but most noticeably down low and above 6000 rpm it doesn't quit making power like the old combo did.
Either way I’d swap to a LS3 top end. Some ported BR3’s and a LS3 intake with a new cam that better suits the powerband and it would make a huge difference.
Either way I’d swap to a LS3 top end. Some ported BR3’s and a LS3 intake with a new cam that better suits the powerband and it would make a huge difference.
Cam is custom specifically for my setup. Just because I want more power doesn't mean the current setup is not performing well. I just don't have numbers on because it hasn't been on a dyno. When I first put this engine combo together I thought it was stupid fast for a daily drive able car. Now I'm used to it and want more...LOL.
06-12-2020, 05:43 AM
Better top end or bigger head unit 
