Need a Reference Verified......

[TC]

I pop into SpeedTalk every so often, usually just to ask engine related tech questions.... One of my resent post was on Cam Specs for my twin turbo motor, a fellow by the name of Mike Jones from Jones Cam Design recommended one of his cams. The Specs are very close to the specs that I was coming up with myself so I would be interested in using his cam, but since I've never heard of Mike Jones or Jones Cam Design I thought I would ask you guys if you've ever heard of him and what kind of reference you could give for him....

[dieselgeek]

You never heard of Mike Jones or Jones Cam designs? I thought you were a big reader.

He's top shelf. But if he finds out you're not going to finish a project you asked him for help on, he'll call you out in public like a chump. be careful asking for help if you're not going to go through with the project, he has a name for those kinds of folks. Mike is a hard ass.

[TC]

You never heard of Mike Jones or Jones Cam designs? I thought you were a big reader.

He's top shelf. But if he finds out you're not going to finish a project you asked him for help on, he'll call you out in public like a chump. be careful asking for help if you're not going to go through with the project, he has a name for those kinds of folks. Mike is a hard ass.

Scott just drop the BS, all my projects will be completed, it's just not going to be on your scheduled.... I asked a question he offered an option, I don't mind spending my money with the guy, I just want to make sure I'm getting a quality piece.... It's always nice to get a little assurance......

[Beagle]

one of the few guys actually grinding their own cams.

[dieselgeek]

Scott just drop the BS

Because Alex always finishes the projects he starts. L M F A O

[Barry Donovan]

one of the few guys actually grinding their own cams.

that would be an awesome job.

I have ideas, simply so, probably like TC..
they don't all center like a trans am race car from the 60s...we keep buying anyway.

anyhoo..if the guy makes what ya want, who cares about reference. Not many make what I want either..

[Beagle]

that would be an awesome job.

I have ideas, simply so, probably like TC..
they don't all center like a trans am race car from the 60s...we keep buying anyway.

anyhoo..if the guy makes what ya want, who cares about reference. Not many make what I want either..

B3M - here's a story from Circle Track magazine that shows some of the process, it's pretty cool.
www.jonescams.com/circle_track_story.pdf

[JeffMcKC]

Mike Jones and I have talked and I have ran one of his Camshafts ( the 08 on the bumper camshaft on Drag Week) I just sent the Green Express truck his way, and The Law (Tom Hogshead) picked up with his turbo cam when I sent him Mikes way. His grinds run very close to the RPM that PipeMax lobes say they will from what I have seen. You will need your flow numbers on your heads.

[Bob Holmes]

And, frankly, for a turbo you need to have an idea of the backpressure. Mike is top notch.

[TC]

And, frankly, for a turbo you need to have an idea of the backpressure. Mike is top notch.

Bob I know that backpressure is something that needs to be addressed, but I won't know what kind of pressures I'll have until I run the motor... One guy over there stated that his 400 with 64mm turbos with .96 A/R had no back pressure.... My turbo's have a .84 A/R, but I also have 50 less cubes than he does, so I'm thinking that if their is some backpressure that it's not going to be that significant.......

And Bob and Jeff thanks for the references, as I do value both of your opinions.... When the time comes I'll give him a call and get this puppy rolling..... First thing I'm going to do is take the block to Rick Watters here in Phoenix and have the block checked out and get his opinion on what I plan on doing...... I do plan on starting this build after the first of the year......

[dieselgeek]

One guy over there stated that his 400 with 64mm turbos with .96 A/R had no back pressure.... My turbo's have a .84 A/R, but I also have 50 less cubes than he does, so I'm thinking that if their is some backpressure that it's not going to be that significant.......

Ignore the guy who claims no backpressure on a turbo system, for without backpressure you make zero boost.

Maybe he meant to say he's close to a 1:1 drive pressure ratio? and even then, you're talking Forumla One levels of engineering. There are some downsides to 1:1 pressure ratios as well especially on a street car.

Measuring backpressure is hard to do accurately also, I've had a hard time and tried it (in reality, not on the internet) 6 or 7 times now.

Presume you will have a 2 or 2.5:1 pressure ratio to be safe. I've seen 3:1 on street cars not too optimized, junkyard turbo setups etc. That means if you want to make 20psi manifold pressure, expect 40-50psi exhaust backpressure.

[TC]

Ignore the guy who claims no backpressure on a turbo system, for without backpressure you make zero boost.

Maybe he meant to say he's close to a 1:1 drive pressure ratio? and even then, you're talking Forumla One levels of engineering. There are some downsides to 1:1 pressure ratios as well especially on a street car.

Measuring backpressure is hard to do accurately also, I've had a hard time and tried it (in reality, not on the internet) 6 or 7 times now.

Presume you will have a 2 or 2.5:1 pressure ratio to be safe. I've seen 3:1 on street cars not too optimized, junkyard turbo setups etc. That means if you want to make 20psi manifold pressure, expect 40-50psi exhaust backpressure.

I reread what he said, I don't think he meant that it didn't have backpressure, I think he meant that he hadn't taken any backpressure readings, so my bad on the interpretation, but he did say not to expect terrible ratios based on similar combos......... Even Vizard said in his book that a 2:1 pressure ratio was on the extreme end of things, he said with the advancements in modern day turbos that the pressures should be way less than that......

As for testing backpressure I don't see it any different than when we used to see if a Cat was bad, just plumb a gauge in between the exhaust manifold and the cat, rev the engine and watch the gauge......... I would think you could use some sort of sensor to do the same thing and data log it with the MS.......

[dieselgeek]

As for testing backpressure I don't see it any different than when we used to to see if a Cat was bad, just plumb a gauge in between the exhaust manifold and the cat, rev the engine and watch the gauge......... I would think you could use some sort of sensor to do the same thing and data log it with the MS.......

First, just revving the engine will get you no boost and no backpressure measurement. A turbo engine needs load and RPM to build boost.

Second, you can use a simple port off the exhaust manifold, some copper tubing to cool the pressure charge, and a simple pressure transducer to feed either a gauge or a logging device. The problem you run into is, you get all kinds of pressure pulses, not a steady signal, so you have no idea what your real pressure is. Some guys have gone so far as designing a "pitot tube" (what airplanes use to measure airspeed), which gets you a real pressure indication. You can't do much with data that spikes to unrealistically high and low numbers, that's the problem I ran into.

I honestly wouldn't worry about it, get it running first then optimize it second.

[Bob Holmes]

If you have any significant back pressure (and pretty much anything over 1:1 is significant) you should be looking to a cam that has zero or negative overlap. Given that having higher pressure in the exhaust will drive exhaust up the intake system and leave you with a contaminated intake charge, you are better off to close the exhaust valve before opening the intake. Given that a turbo will eliminate the exhaust driven "suck" that encourages the fast filling of the cylinder, there is no benefit to overlap in a turbo engine. Use the turbo to fill the cylinder.

Or you can do the big turbo thing, with the big AR and hope to get to 1:1. It will suck to drive and be like a light switch. Only good for the track and generally undriveable. Jeff Goddard, Cosworth's head engine designer during the turbo F1 years, to this day recommends a zero or negative overlap cam in a turbo app, I believe the DV does also.

There is nothing that sucks more than an inappropriately oversized turbo. I'd far prefer something too small and driveable over something oversized that comes on like a light switch.

[TC]

I honestly wouldn't worry about it, get it running first then optimize it second.

That is what I figured I would have to do, get it running see what kind of pressures I have and go from there...

And Bob your right DV does talk about a zero overlap on a turbo cam when backpressures are high, basically close the exhaust at TDC and then open the Intake shortly after, said they made over 1000hp with a 350 with a cam like that........

And thank you guys for the info definitely stuff I'll keep in mind when I talk to Mike......