centrifugal s/c questions

is there anything that can make a centri build boost sooner on a stock engine 3v motor ? didn't do enough research on these and disappointed that for a street car never really get to use the power

smaller blower pulley or overdrive crank pulley

Smaller pulley and a waste gate on the inlet pipe to the IC. Search here I have it somewhere.

Jbarker83 said:

is there anything that can make a centri build boost sooner on a stock engine 3v motor ? didn't do enough research on these and disappointed that for a street car never really get to use the power

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Investigate a wastegated modification to the system. Basically you will pulley it for way more boost than you need, but dump the excess boost to maintain your desired boost. It'll bring boost in much sooner. Centri blowers are linear. More revs = more boost. If you pulley for 25 psi at 6000 rpm you will have plus/minus 12.5psi at about 3000 rpm. At 1000 rpm this would give ~4psi. At 1500 ~6psi. At 2000 ~8psi.

Here is a good start for reading:
https://www.s197forum.com/threads/wastegate-on-procharger.59580/

You will need an experienced tuner to ensure proper function. Depending on the blower you could have 8-10 psi in the low 2000 rpm range and carry that to redline.

my 3v internals are stock i have long tubes and cushman nsr cams with a paxton novi 1200sl 3.33 pulley with paxton air 2 air ic making 544whp and 9.6psi at 6200 rpm tuner said thats to much for a stock 3v torque is around 444wtq manual with 4.10 gears current kit is using 2 bpv

i am just trying to see how i can increase low end power i guess

cant seem to find a how to on going blow thru and adding a waste gate no experience doing that would need custom piping and some help

i see they make a torque booster for the 5.0 to do what i think i am trying to do

The cams likely are contributing to the low end issue as they will just change where the torque peak occurs. As for the limit, the torque number seems to be more of the concern than the HP number so under 450 ft/lbs of torque is considered safe.

As for switching to blow thru, I'm surprised the paxton kit still uses a draw-thru setup. You basically will add the MAF flange to the longest and straightest piece of tubing between the intercooler and the throttle body. Then you can either extend the harness for the MAF sensor or there are a few companies that make an extension harness if soldering wires isn't your thing.
It will need a re-tune for the diameter of the tubing that the MAF is now contained in.

Thats the nature of a centri setup as you have found out. Very top end and don't have peak power until peak rpm. Perfectly fine for drag setup. But very unimpressive on a street car ime, specifically a manual. A stalled convertor auto tends to feel better.

So really you can dona few things none of which will probably give you the feel you want. So off the bat sounds like a PD blower or a small turbo setup would be better up your alley. That would give you more of want your looking for.

I 100% agree about the cams statement above they are sacrificing low and mid for high. The blower already makes more than enough power to peek a rod through the block and makes it all up high. Stock cams are actually very decent with boost on a stock block setup. That will give you more low-end response and bring that peak power down to something safer so thats the first thing I would do.

I would not mess with "torque boosyer" spinning faster and waste gating the setup on a stock block build. Would very small change for the effort and put out a lot more heat.

To recapp cam/ cam timing would be the best way to help well round the setup. Stock or cam with low-end advance like the truck cam.

Jbarker83 said:

my 3v internals are stock i have long tubes and cushman nsr cams with a paxton novi 1200sl 3.33 pulley with paxton air 2 air ic making 544whp and 9.6psi at 6200 rpm tuner said thats to much for a stock 3v torque is around 444wtq manual with 4.10 gears current kit is using 2 bpv

i am just trying to see how i can increase low end power i guess

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If you still have your original stock cams, swapping them back in and getting a retune would be your best solution. You'll lose some peak HP but this will fatten up the torque curve below 5000rpm and improve the whole driving experience.
If you still have the stock charge motion control valves, I suggest you delete them. They're a significant airflow restriction on a centrifugal supercharger set up and you'd gain HP/TQ at medium/higher rpm without any low rpm loss.

Dino Dino Bambino said:

If you still have your original stock cams, swapping them back in and getting a retune would be your best solution. You'll lose some peak HP but this will fatten up the torque curve below 5000rpm and improve the whole driving experience.
If you still have the stock charge motion control valves, I suggest you delete them. They're a significant airflow restriction on a centrifugal supercharger set up and you'd gain HP/TQ at medium/higher rpm without any low rpm loss.

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doesn't the cmcv help with low end torque? i dont want to lose any if i go back to stock cams as thats where i do most of my driving i love the sound of my cams but i guess losing that low end is bothering me since the blower makes plenty up top

Jbarker83 said:

doesn't the cmcv help with low end torque?

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Nope. With a good tune you'll have no low rpm torque loss. Trust me. Deleting the CMCVs was the second mod I did on my car after the JLT 3 CAI, and my butt dyno would have noticed any torque loss right away when trying to pull from low rpm in 5th gear.

I have a positive displacement blower

If I hammer it at lower rpms in the wrong gear around 2000 rpm, the car does not move out. It feels like dog shit.

There is no magic low end torque. If I had a centrifugal, I would maybe change rear gears, or think about going to a close ratio gear box. I think the centri blowers deal a lot less with heat issues, also. No enormous 100 lb chunk of aluminum heat soaking and heat soaking the sensor on top of the engine.


***I also think I may underestimate things, at part throttle the blower does work great at lower speeds. I can see how a centri won't do anything. Again - gears and gearbox. Get the engine spinning.

well just got the delete plates and going to put stock cams back in get another dyno tune hope that improves low to mid performance

Jbarker83 said:

well just got the delete plates and going to put stock cams back in get another dyno tune hope that improves low to mid performance

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If it doesn't I'll eat my hat.

Centri blowers do matter even off idle without any boost registering on the guage. I know this for a fact.

My first blower was a Powerdyne. I was at Watkins Glen for an HPDE event with my 91. The Powercrap blower blew the inside belt. I finished the event NA with the blower belt removed. On the 300 mile drive home, I realized I had lost a significant amount of torque in the idle - 2500 rpm range. This was with a HCI setup with the e303 cam. Centris dont make the instant torque a PD blower does, but they do add torque. On went the Vortec and 15+ years later, still running strong.

Just thought Id share..

Juice said:

Centri blowers do matter even off idle without any boost registering on the guage. I know this for a fact.

My first blower was a Powerdyne. I was at Watkins Glen for an HPDE event with my 91. The Powercrap blower blew the inside belt. I finished the event NA with the blower belt removed. On the 300 mile drive home, I realized I had lost a significant amount of torque in the idle - 2500 rpm range. This was with a HCI setup with the e303 cam. Centris dont make the instant torque a PD blower does, but they do add torque. On went the Vortec and 15+ years later, still running strong.

Just thought Id share..

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Very true,
The torque loss in your case was partly due to the resistance of the air needing to get by the impeller but you are definitely correct that even though the compressor is not moving fast enough to compress the air, it is certainly assisting getting air into the motor.

Actually, it ran really well on track just breathing through a non-spinning blower, surprisingly. I was not expecting the powerloss so noticable down low.
Oh, max boost was just under 8psi btw, just for reference.

here is my current dyno chart

mods are cams/long tubes catted x/ paxton 1200sl intercooled 3.33 pulley/4.10 gears manual car

it was detuned from 544/474 above 4800 is where it got more power otherwise both look the same

Dino Dino Bambino said:

If it doesn't I'll eat my hat.

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posted my dyno graph take a look let me know if you see if the cams are affecting it

here is the max power dyno graph that we detuned to the graph above tuner says his dyno reads torque about 30whtq higher than it is both 93 pump gas

You have a nice spread of torque with the curve being virtually flat from 4300-6200rpm. The stock cams & CMCV delete will fatten the curve below ~5000rpm. You'll probably see a small increase in peak TQ and with the peak shifted lower in the rpm range. At 6200rpm you should still have over 500rwhp.