Pizza

I didn't expect this many replies when I started this thread. It seems like a lot of people are waiting to see what happens with your day at the dyno Woody. Including me. My next thread might start like this: 86.5 Twin Screw with headers and custom exhaust now at 450 RWHP. Or maybe like this: For sale, Devek Level II 1 3/4" primaries headers Jet Hot coated, brand new, never been used. Come on Woody, make my day!!!!!

hacker-pschorr

Not sure if this makes a difference. What kind of supercharger are you plotting into the system here? With a flat boost curve between 2,500 - 4,500 rpm.

Vlocity

Speaking of blow through....here is a pic of my car running at Beaver Run just a few weeks after the inital install. Pretty Rich........

Also, with regard to Woody's comment on the air filter being to small I believe that is 100% true. I did some research and enlisted the help of a tech at K & N and he determined that the engine required around 875 CFM. (There is a basic formula available on their web site, but it did not have a component for boosted engines.) 875 CFM requires a filter with 146 square inches of surface area. I have purchased a filter that will flow over 975 and plan to build a "bridge connector" over the radiator and place the filter in front. Below is a link for the filter that I have and plan to use.

http://www.knfilters.com/search/prod...x?Prod=RF-1034

My work will start this weekend as I am bringing the car home out of storage and have all of the ingredients here to start the mockup.

Regards,

Ken

Louie928

It was a Roots style (the only pos disp choice) with the efficiency bumped up to be equivalent to the TS.

hacker-pschorr

have you ran the same test with a centrifugal?

Louie928

No, I didn't. There is a Vortech V2S choice. I'd need the belt ratio.

toofast928

Great thread!
I ran exhaust back pressure test last year on my 16v. Powerdyne installed, 9psi boost, non I/C. Borla 2 1/2 cat back exhaust system.

With test pipe installed no cat, Had loss of bottom end power but revs were quick and felt faster 5000 RPM
With a single 3" catalytic converter exhaust back pressure was 10psi. Bottom end power returned but engine was being starved for air. Lot's of engine braking on deaccel.

Next installed an X pipe, splitting the catalytic converter, two ovals 2 1/2". Best of both worlds. Great power at low revs and easy to rev to 6000 RPM. Exhaust back pressure 4 psi.
Max boost at 6000 RPM droped to 6.5. Good... engine is using more air.

Then I tried fooling around with the Car-Tech exhaust baffles. 3 disc then 2 disc. They quiet the exhaust nosie to a mouse levels but not worth the added back pressure. Actually lost power when installed.

Now thinking about headers but cost of headers plus cost of changing rest of the exhaust system may not balance out. For street use, how much more HP would headers give me with cats installed?

hacker-pschorr

You could install 85-86 exhaust manifolds (same units Louie is using for this testing) and not change anything else. You would need an extention, about an inch and a half on the passenger side.

Louie928

I ran EAP with a centrifugal. The choice was a Vortech V2-S trim. There is a lot of spec that can be entered for the centrifugal such as island flow, island pressure ratio, island efficiency, mechanical friction, internal gear ratio, all of which I know nothing about. I used the default values that were already in the program. I chose a drive belt ratio of 1.75:1 which gave about 8.5 - 9 psi at 6000. Results were interesting as compared to the TS. The torque curve is naturally different (not as flat) since the boost isn't as constant. The big exhaust hurt the lower end a lot while on the TS it didn't make much difference. The top end responded a bit better with the Vortech. The boost levels didn't change much regardless of which exhaust as opposed to the TS which lost about a pound of boost above 5000. Remember though that this is just an approximation, and the results depend a lot on the configuration specs I entered. Even though both the TS and Cent. SC, and exhaust specs probably weren't spot on accurate, the trend is probably close to what you could expect.

As sort of a conclusion, I think when contemplating an exhaust change with a supercharger, it would be valuable to first measure the exhaust backpressure. If it is below around 2 - 3 psi, don't mess with it. If above 4 - 5 psi, you might see some gain by freeing up the exhaust. With a TS, expect to change pulley ratio to regain lost boost and realize the performance gain from the exhaust. Careful with a centrifugal SC, or you'll lose the low end.

https://rennlist.com/forums/attachme...d=179952&stc=1
Exhaust diff with Vortech.jpg

all4woody

Went to the Dyno in B'ham last night, nice facility with smart people. I did 3 pulls with the filter on (I was going to take it off for one pull but forgot) and baffles set at their middle setting. I am at work so I can't post my chart, but will soon. If I remember correctly:
458rwhp
458rwhp
461rwhp
all with 420-430rwtq
I will change the baffle to it's most restrictive setting and run again when I get back from HI.
Later, Woody

Pizza

I recieved my headers to head gaskets yesterday. I'm at a point where I need to do something so I can get my Motor mounts installed and put my car back together. I'm thinking about going ahead and installing the Devek headers and modifying my Ott X pipe to them with my stock 2 1/4" exhaust after that. I could always play with the exhaust later. Would I benefit at at from just the headers?

all4woody

Here is the dyno from last night. 8.5psi with baffles in exhaust.

all4woody

Louie,
Where should my fuel be? I have heard 13.5, but the tech last night said that was too lean for forced induction. Any thouts on this?
Thanks, Woody

928SS

I wonder if you are just maxing out the MAF w/more flow.

Tony

Guarentee that. Its was probably pegged a long time ago.
You have a super MAF Woody? or a Sharktuner?