tyoneal

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James: Do you know if a "Blow off valve" is what I would need?
I've been told the terminology changes in some cases between the Superchargers and turbos, for an item that essentially does the same thing.
Thanks,

Ty

WOT: would be used maybe 10-15 seconds max at a time then go for long periods at 1500-2000 rpm on the highway.

James B.

iTrader: (1)

They're blow off valves. The BOV in a turbo kit relieves the intake of pressure when the throttle closes in order to prevent pressure surging in the compressor wheel. With turbos it's the waste gate that controls boost acting as a bypass for the exhaust to get around the turbine without doing work. With a turbo you control compressor RPM and output but with a centrifugal supercharger the compressor output is fixed to relative engine RPM. The blowoff valve has be progressing and fast-responding. ProCharger and Vortech both have them available.
I can't suggest a pulley size until we have a reference for what boost its making now.

tyoneal

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James:

Thanks again for your help.

All that does make sense. Given the engine size and what the Air / Fuel demands would be at a much earlier RPM. (2000) I'm wondering if the unit can spin up fast enough without the belt slipping.

I guess if I was **** enough I could always add a small turbo for the early power and have a hybrid?

I'll try and get all the information Monday, possibly tomorrow if I can.
Thanks,

Ty

tyoneal

James:

I re-read this post and it was mentioned:

Assuming a 5800 engine RPM limit imposed by the hard ceilings in the PCM, you can safely run down to a 2.88" pulley on the blower without overspinning it. At some point belt slippage is always eventually a consideration with smaller pulleys but I think at 3" you'd be fine.
In other word, you've got plenty of room to grow with your current blower!

What is the formula calculating the amount of boost at a given RPM?
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Would this be a reasonable approach to my problem?
(I wanted to try and think this through with you to see if I have a decent grasp of this process)

Take the known boost at a given RPM, then take the percentage of extra speed a 3.0, or 2.88 inch pulley would spin an impeller shaft over a 3.35 inch.

Take the percentage, multiply it against the current (3.38 inch) and calculate the boost w/o a blow off valve.

Once done, a similar curve drawn on the current Dyno sheet can be (might be?) drawn to get a hypothetical boost curve. Calculated with a 2.88 and a 3.0 pulley.

Find the curve that most closely estimates the desired amount of boost at a earlier RPM, then switch and retune to the new pulley adding a preset Blow-off valve to mitigate over boosting the engine under the desired Maximum RPM Range.
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Would these smaller pulleys move the boost curve up 12%-16%?
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Thanks for your patients again, I really want to understand the art of Boosting an engine.

Ty

James B.

iTrader: (1)

There are too many variables to determine what the boost curve should be. It's probably possible to get close but literally everything that effects induction or exhaust efficiency will have an effect on boost. I have flow numbers for your engine that are likely to be fairly close to what it actually makes, but we still have no reference point.

For example, I've been involved in several discussion over the years with people who had concerns they lost power because they noticed a drop in "boost" after upgrading the exhaust, heads, or cam. Their mods made the same engine displacement flow air more efficiently and therefore put up less resistance to the intake charge = lower manifold pressure but more power.

Am I right in assuming you've got a supercharger kit that was designed and sized for a stock Vortec 454? You've got more displacement, much better flowing heads and exhaust, larger cam and a ported intake. At some point the device that's supposed to be assisting air getting into the engine begins to restrict it. The Supercharger needs modification to compliment the much more capable engine it's feeding.

When you had it dyno'd, did they log manifold pressure? If the supercharger still has the same pulley on it included with the 454 kit then I doubt it's even making 6psi at maximum RPM. Would really like to know how much boost at an RPM point it's making. Earlier in the thread it was mentioned that peak power is at 3800RPM. That seems a tad low. The simulations I did put it between 4000 and 4500. How much boost is it making at the moment it hits its torque peek at 3800?

Is it possible to get a wide open run on video? Need to be able to see both your boost gauge and the tachometer clearly in the frame. Fixed mount for camera (Go Pro, etc.) would be great so freeze-frames are steady and clear. Fixed mount would be safer too.

Also, it is not going to need a blow-off valve until it starts getting past 10psi. I really doubt it's even coming close right now.

tyoneal

James:

Thanks again for your time. Here are some answers to your questions. (I'm sorry I don't have everything you asked for yet.

There are too many variables to determine what the boost curve should be. It's probably possible to get close but literally everything that effects induction or exhaust efficiency will have an effect on boost. I have flow numbers for your engine that are likely to be fairly close to what it actually makes, but we still have no reference point.

For example, I've been involved in several discussion over the years with people who had concerns they lost power because they noticed a drop in "boost" after upgrading the exhaust, heads, or cam. Their mods made the same engine displacement flow air more efficiently and therefore put up less resistance to the intake charge = lower manifold pressure but more power.

Am I right in assuming you’ve got a supercharger kit that was designed and sized for a stock Vortec 454? YES

You've got more displacement, much better flowing heads and exhaust, larger cam and a ported intake. At some point the device that's supposed to be assisting air getting into the engine begins to restrict it. The Supercharger needs modification to compliment the much more capable engine its feeding.

When you had it dyno’d, did they log manifold pressure? I don't know. I spoke with the tuning shop and they will get these numbers for me. I have so many questions and the Dyno sheets I have just don’t allow the truth to be uncovered easily. I’m going to try and get a lot of information about the dyno pulls, and if possible have the date loaded on a thumdrive for me so things during the different pulls can been analyzed.

If the supercharger still has the same pulley on it included with the 454 kit then I doubt it’s even making 6psi at maximum RPM. AgreedEmbarrassing, I don't know, I'm sorry.

Would really like to know how much boost at an RPM point it’s making.

Earlier in the thread it was mentioned that peak power is at 3800RPM. That seems a tad low.

That was using the stock EFI intake with the 65 psi injectors. I discovered its maximum flow was 640 cfm. (I know this was a stupid mistake to make, an I admit this freely, its my first time dealing with a boosted engine. I did a Volumetric Efficiency Equation and came up with a need of 1200 cfm +/-. It was with the STOCK 640 cf. intake that 3800 rpms was the peak.

I changed to a Vic jr. intake and a Fast 4150 TB, which I thought should be a nice fit for the engine.

It was after this change that the peak rpm shifted to 5750 rpm +/-, 416 hp/ 462 tq rear wheel power. These values were flat from 5750 rps through 6300 rps, however at 4750 rpm hp/tq was 280 hp/310 tq rear wheel power.

At 5250 rpms, where the hp = tq the value was 362 hp/tq.

All the real usable power is so high it would never come close to being utilized.

Until I get more information maybe this will help.


The simulations I did put it between 4000 and 4500. How much boost is it making at the moment it hits its torque peek at 3800? I will get these numbers.

Is it possible to get a wide open run on video? Sure, I will get that for you as well.

Need to be able to see both your boost gauge and the tachometer clearly in the frame. Fixed mount for camera (Go Pro, etc.) would be great so freeze-frames are steady and clear. Fixed mount would be safer too.

I have all the gauges bought, however I have not got them installed yet. (I known I’m not helping in this department, but I needed my truck and some extra $$$ tp get these installed.

Did you mention some of the Gauges run off of the Transmission? If I upgraded the ECU/PCM/CPU what would I have to worry about with the rest of the truck?

I have 32 inch tires on this which are not light. I noticed I had a number of heavy extra parts in the rear. I'm thinking some of the power loss is due to the weight addition.

This said, the relative slowness that the boost appears to kick in is a huge factor. Given the extra airflow of this new engine, as you said, the actual boost levels could absolutely be very low, AND that would be a good reason for the power to shift 1800 rpm's further out.

I think we are making progress.

I'll get more and look forward to hearing from you.

Thanks again,

Ty O'Neal

I wrote the above message very late/early yesterday morning and forgot to post.

I wanted to mention to you that I have learned a ton of sound logical information in this thread, and am starting to really get an insight into the area of performance.

Thank you

The Pulley as far as I've been told was the one that came with the "Kit". (3.35) The guy I worked with left the firm and so I will have to go visit and get on their computer to affirm. (Hoping that they still have the information)

This said given the known value of VE in the stock engine is (Next Page)

James B.

iTrader: (1)

Ahh there it is. The pulley is absolutely without any doubt at all the problem.

Think about it - the supercharger is moving nearly the same amount of air as it would be on a stock 454 which is why your engine is making nearly the same numbers as a stock 454 with this supercharger kit would.

Before expending effort on anything else you've got to get that boost gauge installed. I thought you already had one - they are essential items with any sort of forced induction. It was never clear to me why you had no boost numbers - no gauge! It all makes sense now.

We're going to pulley the hell out of that thing. Get the gauge installed...

My guess is it's making a whopping peak of 4 psi.

tyoneal

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James:
I spoke with Pro Charger today to get some information of what the stock pulley size was that came with my kit.

They told me the stock pulley is a 3.55 inch, I now have a 3.35 on it, so it must have been changed.

They also told me that for every 10th of an inch smaller the pulley goes, it increases the boost 1 psi.

The lowest they supply is a 3.0, however I'm sure smaller ones can be found.

Once you go below 3.0, they recommended using an overdrive crank pulley. They said to keep tabs on how that affects the other accessories on your engine. They too may require a pulley change to not over-rev everything else.

If 10 psi is a 3.55 pulley on a stock engine. Then a VE of almost double then you would need the equivalent of a 2.55 final drive with which ever combination of pulleys that can be found.

Is this in the right direction or possibly close?

Thanks,

Ty O'Neal

tyoneal

James here is a link that really brings all this together.

ATI DPxxx ProCharger Pulley 6 Rib and 8 Rib

Notice that the crank pulley with the 6 Rib Belt is a 6.0. It is 7.5 with a 8 rib belt.

It appears like I will probably need to go to a 3-core intercooler, as the 2-core seem to max out at 550 hp (assuming crank hp) The 3-core get you up in the 8-900 hp range.

http://shop.brutespeed.com/ATI-04-06...?categoryId=-1

Thanks,

Ty

Y2KLimited

thinking back to 13 years ago when I had a procharger on the tahoe's stock 350 with the 2 core it was maxed out with the provided pulley (when I dropped 2 sizes I saw no gains in boost, yet it was enough to take out a head gasket) That very well can be your dilema, procharger has a habit of cheaping out up front to keep costs down hoping everyone will stay with a stock pulley.

I'd lean towards the intercooler, it realistically can't hurt.