fast951

Josh, Backpressure is exhaust pressure between the head and the turbo. You are looking for a ratio between boost pressure vs. exhaust pressure. You can measure backpressure by attaching a boost gauge to the test port on the cross over pipe. Make sure to use a few feet of copper pipe between X-over and gauge.
Not sure if I can make it this weekend, but will try to make the drive.

Josh B

I've got the clear lenses to replace the orange on the rear lights - just have been putting off that job.

I've been admiring your car in the pics I've seen - looks really clean and those wheels are sweet!

Judson951

What numbers should a person look for?

fast951

There is not a preset number, it's a ratio. You must stay below 2:1 (Exh:Boost).
The lower the better (1.2:1 is a very good number). The ratio changes with boost.

Josh B

Sorry to pick your brain john but does this graph sort of show what you are talking about? Wouldn't the exhaust gasses melt a guage pretty quick even with some copper tubing?

cruise98

Josh:

I did not see the 3.0 FPR or an adjustable FPR on your list. Also, i would install the injectors that the chip board is mapped for and take it from there.

Have you determined if the wastegate is working properly?

Josh B

Hi Keith - I've got a 3.0 FPR on there and a manual black **** boost controller. When I had the 65lb injectors in the car the AFM number was off the scale below 10 on WOT under boost. When I put the 55lb injectors in the AFM was closer to 11 under the same conditions. I think once I get the SMT6 back on I can swap the 65lb injectors back in and tune the car based on them. I suppose I should get them bench tested first though.

I haven't done any tests to the wastegate but I did order new gaskets for it yesterday.

944CS

I don't like the lindsey intake, why did you go with it?

Josh B

I actually only have it because I picked up a parts car that it was already installed on. In fact most of my mods came off that car - hard pipes/tial/head/blow off/intake/sfr exhaust/modified intake/fuel lines/ignition wires.

944CS

I would sell it and use the money you make to extrude hone your stock manifold

Josh B

Hmm - I would have to pick up a stock manifold. What do you think the dis-advantages and advantages are to each route? Have you had some experience with the lindsey intake as well?

-Josh

944CS

from a design standpoint it is not optimal, any advantage it has over a stock manifold can be corrected for less money than buying a new one

Josh B

I am sure you are onto something with that. I am really inquisitive about how someone would measure the characteristics of an intake? I suppose you could do a dyno and some sort of flow testing? What the numbers involved? Do you want the air to be evenly distributed to each cylinder, do you want it to get there quickly after leaving the throttle body? Do you want a large storage of air in the body of the intake, do you want the air to develope some turbulance - be insulated from the top of the engine, etc?

Josh B

Actually all the answers to my questions are probably in this thread or the links on it...

https://rennlist.com/forums/924-931-944-951-968-forum/368943-951-custom-intake-manifold.html

In any case I'll probably keep the intake for the following dumb reasons

1. I like how it looks
2. It is easier to get on and off than the stock intake
3. I can see what is going on underneath it better
4. It may allow a little better airflow around the engine
5. It has 5 holes tapped into it where I can pull vaccum easily and my brakes seem to work better
6. I didn't have to fork over $1400 for it new - basically got it for free since I already made my money back on the parts car.

blown 944

You would use a flowbench and measure the volume of air at set parameters.

You can measure overall flow at max valve lift and get an idea of the velocity at lower lifts as well.

the larger the area after the Tb (with all else being =) the lower the TQ

what you want, is a flow that is at peak flow at the max cfm required per cylinder. If you have a much greater volume than required you are losing tq.

Moreso you want equal flow to each runner to prevent lean/rich cylinders