Supercharged 7.3

superpsd · Jul 13, 2014

I will be adding a boost/vaccum gauge on the discharge side of the intercooler feeding the turbo. I was going to add it today but the tap I need is at work in my toolbox. So tomorrow it is. I fixed a boost leak a clamp was not tight enough and a coupler wiggled back. Fixed that and test drove it. Boost is still laggy but there is definitely already a n increased response on the stock tune. I won't be flipping the switch until I can see what the pressure or likely vaccum is pre turbo and I will be ordering a 2.5" pulley for the Eaton tomorrow giving me a 2.7:1 blower ratio. Then in a little while I will be bolting on the direct replacement 2.9L whipple "1900 cfm capable". I checked all fluid levels today and everything is great. Truck is pulling strong. Now it needs to spin much faster. The intercooler is doing it's job. My IR thermometer is seeing a 35-40 degree difference from pre-IC and post. I also have a large bypass valve to install and hook up to let the turbo take over once lit up.

My toy funds are all dried up as I just got married at the cost of over 15k. So it's going to take a few weeks to buy a $ whipple $ otherwise one would be already on the way

Charles · Jul 14, 2014

The blower you have is plenty big post-turbo, as the 7.3 only consumes 300 or so CFM in the rpm range we deal in. The blower you have would keep steady pressure on it if not for it trying to blow into a charger that's inhaling 5 to 700+ CFM instead.

The cart would work better behind the horse. Course two horses are faster than a cart and a horse anyway. Sell the blower and grab a T6 charger instead. Response is only limited by available traction in that case.

superpsd · Jul 14, 2014

I consulted with Crazy Carl a guy who builds and sells Whipple kits for the Cummins crowd. He has built setups both ways and has found that the blower over the turbo is the most effecient way to go. He did say a bypass is necesarry to let the turbo take over when the suction over comes the flow from the blower. In these setups they are seeing increased response, less smoke, lower egts, elimination on lag between shifts on a manual trans equipped truck, and quicker cool off shutdown times.

I drove my rig to work and back last night and even with a low boost you can already feel the difference normal average acceleration from 1000-1500 is smoother that I have ever felt it on the stock tune. I ordered an 2.5" pulley this morning. I will see soon how well it improves the speed. It should be the ticket. My current setup drives the blower at 2.25:1 the 2.5" will spin the blower at an ratio of 2.7:1. Current blower speed @ 650rpms is 1462.5 rpms and will jump to 1,755 rpms. Rpms @ 2000 is currently 4500 and will jump to 5400. At 3500 rpms the blower will be @ a maximum speed of 9450.

The Eaton is big enough but a whipple is a far more effecient blower that will be more versatile. I am limited to a 2.5" pulley on the Eaton without expensive machining of the snout to accept a smaller pulley. I would have to build a dual piggy back pulley drive to gain more blower speed. A whipple will flow more air at a lower speed lowering intake temps and overall efficiency. Not to mention a smaller pulley can be more prone to belt slippage at higher loads.

superpsd · Jul 14, 2014

Well gauge is installed. Pressure is 1-2 psi pre turbo no matter how hard you stab it. It maintains 1-2 psi off idle up until 2000 then the gauge goes left to 1-3" of vaccum. So for now I will keep it under 2000k as my short drive to work and back is flat ground. I will just baby it until the pulley arrives.

2000wa250 · Jul 15, 2014

Pulley will not change the vacuum IMO....I'm a bit fuzzy, so.could.someone remind me what 1-3" of vacuum roughly translates into psi?

I don't see how 1000 more rpm out of the blower on average will build enough psi to give you a positive pressure in front of the turbo...

If you respond with your goal isn't to use the blower as a true compound, but instead are simply using it for better throttle response, you could have saved a ton of time, money, and pain in the ass by simply putting a tighter housing on your turbo

superpsd · Jul 15, 2014

I do have positive pressure at the turbo inlet. 1-2 psi until 2000rpm. Adding a smaller pulley will push more air creating more pressure.

For every revolution of the blower it pushes 122 cubes of air or 2.1L. Turning 1000rpm more makes all the difference. I never said this was a compound setup. I stated from the start this is to improve response , drivability, reduce smoke, lower egts. A bypass will be needed when the turbo takes over. Also the whipple is the goal in the end. The Eaton flows a maximum of 865 cfm the whipple I plan to upgrade to has a maximum capability of 1900cfm. That is double. Why would I want to neck down and restrict the turbo further? A smaller snail will increase drive pressure and increase eggs in the higher operational range. Not to mention if I do opt to latter install bigger sticks the smaller scroll now becomes an restriction. With a positive displacement blower you can run a larger turbo and not have the negative effects such as smoke , eggs, turbo lag...

TyCorr · Jul 15, 2014

Your turbo came with eggs?

superpsd · Jul 15, 2014

Egts. Anyways I pressure tested my charge plumbing and intercooler. I disconnected the elbow going to the turbo and dead headed it with duct tape and poked a 1/2" hole. Used the blower to pressurized the plumbing to 5psi and looked for leaks. Everything is sealed up tight. Just need that pulley now.

superpsd · Jul 22, 2014

Pulley is installed. I see 1lb of boost at idle. I have seen up to 5 lbs pre-turbo which changes with load due to the suction of the turbo. Will hold pressure on turbo inlet past 2500+ rpm on flat ground. Hill s loading the turbo on the higher chip settings will create a vaccum up a hill. Still lots more tweaking to do. Will need to install a bypass. Wish I could spin the blower faster but without crazy modification I see no point I will just save for the whipple. The truck definitely feels responsive down low.

PDT1081 · Jul 22, 2014

superpsd said:
Pulley is installed. I see 1lb of boost at idle. I have seen up to 5 lbs pre-turbo which changes with load due to the suction of the turbo. Will hold pressure on turbo inlet past 2500+ rpm on flat ground. Hill s loading the turbo on the higher chip settings will create a vaccum up a hill. Still lots more tweaking to do. Will need to install a bypass. Wish I could spin the blower faster but without crazy modification I see no point I will just save for the whipple. The truck definitely feels responsive down low.

If I understand what you are saying, when you install this bypass thing, you will still be using power to spin the blower but not seeing any benefit from it whatsoever?

superpsd · Jul 22, 2014

Power to spin the blower is determined on load. The increased outlet pressure creates a load and robs hp. There are actually charts for this but have not looked up the m122 drive power as of yet. The bypass will allow unrestricted air to the turbo when the turbo suction pulls more than the blower can push. An Eaton roots blower make no internal compression. It only makes pressure by flowing more air than the engine can ingest. A twin screw like a Whipple or Ken Bell does compress some of the air charge internally. A whipple will use less hp to drive the blower. The drag resistance internally is less and the effeciency ratios are much higher.

Hotrodtractor · Jul 23, 2014

superpsd said:
Power to spin the blower is determined on load. The increased outlet pressure creates a load and robs hp. There are actually charts for this but have not looked up the m122 drive power as of yet. The bypass will allow unrestricted air to the turbo when the turbo suction pulls more than the blower can push. An Eaton roots blower make no internal compression. It only makes pressure by flowing more air than the engine can ingest. A twin screw like a Whipple or Ken Bell does compress some of the air charge internally. A whipple will use less hp to drive the blower. The drag resistance internally is less and the effeciency ratios are much higher.

So essentially it does exactly what many of us said that it would do when you first posted up. Imagine how far along you would be if you would have listened and discussed this when the concept that the blower was way too small to setup in an effective fashion was first mentioned instead of just assuming that we knew nothing.

FWIW - I'm glad that you have it up and running and now see exactly what we were describing to you and do wish you the best of luck with future changes that could potentially make it work closer the way you want it to.

Charles · Jul 23, 2014

Do nothing but swap the blower discharge from the turbo inlet, to the engine instead, and turbo discharge from the engine, to the blower inlet instead and stick your stock airbox back on the turbo inlet.

The blower will make boost down low and the turbo will spool quicker and make power up top. No new pulleys, blowers or anything else needed.

Just drive around for 5 min that way. That's all it will take. Hell, 30 seconds under power and all will become clear.

TyCorr · Jul 23, 2014

Yea, really, its pretty much that simple. I would at least give it a shot. But Id want the truck to rip if possible. This setup seems to be for people who dont like using the throttle to begin with.

No offense, op, but if you'd try to feed the blower you'd have one of those "oh shti" moments and realize.

Freightshaker · Jul 23, 2014

Charles said:
Do nothing but swap the blower discharge from the turbo inlet, to the engine instead, and turbo discharge from the engine, to the blower inlet instead and stick your stock airbox back on the turbo inlet.

The blower will make boost down low and the turbo will spool quicker and make power up top. No new pulleys, blowers or anything else needed.

Just drive around for 5 min that way. That's all it will take. Hell, 30 seconds under power and all will become clear.

Isn't that how some of the Detroit diesels were factory?

silverpsd_06 · Jul 23, 2014

Why are we re-inventing the wheel? Blow supercharger to motor blow turbo to supercharger.. Voilla problem solved no more vacuum in between stages, all the responsiveness you wanted and no more money to be spent on pulleys/chargers to boot!