Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Forums > Porsche Forums > 911 Engine Rebuilding Forum


Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
3 restos WIP = psycho
 
kenikh's Avatar
 
Join Date: Feb 2005
Location: North of Exit 17
Posts: 7,665
Brain dyno - trying to decode lobe centers and durations into HP

I was just looking at a post on the Early S Board from a 906 engine owner. His car, running the same ‘69S heads as mine, using 906 cams, returned 210 HP on a dyno at 7800 RPM. My car is a 2 liter S that is being seriously tarted up.

I just bought some cams from camgrinder that met the drivability and rev range characterstics I gave him to work with. I am trying to use the brain dyno to figure out how much power to expect on top of the power band. I am not concerned about anywhere else in the rev range, as these cams are going to make significantly more HP and Torque sub-4000 RPM than 906 cams due to having very fast ramps.

Looking at the 906 cam, it generates significantly less lift than the custom DC44:
906= .463"I/.460"E
DC44= .490"I/.490"E

The 906 runs on a lobe center of 96 vs. the 102 of the DC44.

The 906 runs durations of:
290I/262E @ .040" and
283I/255E @ .050"

The DC44 runs durations of:
264I/254E@ .040" and
258I/248E@ .050"

Since top end HP is essentially a function of how much and how fast you can get air into the motor, I am wondering if anyone with more experience than me has a guess as to how much HP this motor is going to make at 7800 RPM on the DC44 cam, using the 906 info as a baseline. A real dyno run will come at a much later date.

Thanks!

__________________

- 1965 911
- 1969 911S
- 1980 911SC Targa
- 1979 930
Old 06-30-2006, 09:55 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
3 restos WIP = psycho
 
kenikh's Avatar
 
Join Date: Feb 2005
Location: North of Exit 17
Posts: 7,665
BTW, assume the same CR.
__________________

- 1965 911
- 1969 911S
- 1980 911SC Targa
- 1979 930
Old 06-30-2006, 09:59 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)
Registered
 
Join Date: Jul 2001
Location: Portland Oregon
Posts: 7,007
Kenik:

Before I'd venture an educated guess, more information is required.

Heads: stock '69S ones?

Stock-type heat exchangers?

Muffler?

'69 MFI?

Twin-ignition?

CR?

Answer all that and I'll offer something based on similar combinations.
__________________
Steve Weiner
Rennsport Systems
Portland Oregon
(503) 244-0990
porsche@rennsportsystems.com
www.rennsportsystems.com
Old 06-30-2006, 01:41 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)
3 restos WIP = psycho
 
kenikh's Avatar
 
Join Date: Feb 2005
Location: North of Exit 17
Posts: 7,665
Stock HEs for now; eventually going to headers by George
Muffler is stock for now; something VERY special later (assume megaphones, coupled with the above headers)
'69S MFI
Twin plug: 10.3 - 10.5:1

Feel free to email me on the "muffler" if you are curious.
__________________

- 1965 911
- 1969 911S
- 1980 911SC Targa
- 1979 930
Old 06-30-2006, 02:39 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)
Registered
 
Join Date: Jul 2001
Location: Portland Oregon
Posts: 7,007
George's headers are too short for these motors,......

Megaphones without a crossover kills bottom and mid-range manners. The effects are exacerbated by longer duration cams.

Any other internal mods? Boattailing? Knife-edged crank?
__________________
Steve Weiner
Rennsport Systems
Portland Oregon
(503) 244-0990
porsche@rennsportsystems.com
www.rennsportsystems.com
Old 06-30-2006, 02:57 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #5 (permalink)
3 restos WIP = psycho
 
kenikh's Avatar
 
Join Date: Feb 2005
Location: North of Exit 17
Posts: 7,665
George's headers are too short? I was assuming he could make them to spec. Let's assume a crossover pipe; since the new exhaust is going to custom fabricated, all is possible.

I wasn't planning on boat tailing or knife edging this motor.
__________________

- 1965 911
- 1969 911S
- 1980 911SC Targa
- 1979 930
Old 06-30-2006, 03:01 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #6 (permalink)
 
Registered
 
Join Date: Jul 2001
Location: Portland Oregon
Posts: 7,007
George makes one length in these 1.5" headers but he does do a custom version for us, exclusively. You can use his standard one, but you give up some mid-range power.

All in all, I'd expect somewhere around 190-195 HP if you have good flowing heads.
__________________
Steve Weiner
Rennsport Systems
Portland Oregon
(503) 244-0990
porsche@rennsportsystems.com
www.rennsportsystems.com
Old 06-30-2006, 06:59 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #7 (permalink)
3 restos WIP = psycho
 
kenikh's Avatar
 
Join Date: Feb 2005
Location: North of Exit 17
Posts: 7,665
Sounds like I will be buying my headers from you then. Thanks for the feedback. It is actually almost exactly what I hoped.
__________________

- 1965 911
- 1969 911S
- 1980 911SC Targa
- 1979 930
Old 06-30-2006, 08:52 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #8 (permalink)
Registered
 
Join Date: Jul 2001
Location: Portland Oregon
Posts: 7,007
Let me get you a copy of the dyno overlay that shows the HP/torqu differences between the short (normal) and long-tube headers on some 2.0 litre race motors that are configured closely to what you are building.

You'll see what I mean,....
__________________
Steve Weiner
Rennsport Systems
Portland Oregon
(503) 244-0990
porsche@rennsportsystems.com
www.rennsportsystems.com
Old 06-30-2006, 09:27 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #9 (permalink)
3 restos WIP = psycho
 
kenikh's Avatar
 
Join Date: Feb 2005
Location: North of Exit 17
Posts: 7,665
Sweet! I can't wait!
__________________

- 1965 911
- 1969 911S
- 1980 911SC Targa
- 1979 930
Old 06-30-2006, 09:34 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #10 (permalink)
Registered
 
Join Date: Mar 2005
Posts: 743
This matter of headers is interetsting, Steve.

I'm assuming you are using 1 1/2 inch pipes?

I wonder whether , with somewhat more rev-oriented cams, eg DE 60's, 1 5/8 with shorter pipes may give a little more in a racer?

Also must decalre an interest!

Kind regards
David
Old 07-01-2006, 05:48 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #11 (permalink)
up-fixing der car(ma)
 
YTNUKLR's Avatar
 
Join Date: Aug 2002
Location: Fremont, CA
Posts: 3,762
Garage
Send a message via AIM to YTNUKLR
must...subscribe...
__________________
Scott Kinder
kindersport @ gmail.com
Old 07-01-2006, 11:35 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #12 (permalink)
Registered
 
Join Date: Jul 2001
Location: Portland Oregon
Posts: 7,007
Quote:
Originally posted by davidppp
This matter of headers is interetsting, Steve.

I'm assuming you are using 1 1/2 inch pipes?

I wonder whether , with somewhat more rev-oriented cams, eg DE 60's, 1 5/8 with shorter pipes may give a little more in a racer?

Also must decalre an interest!

Kind regards
David
Hi David:

Yessir,....these smaller engines; 2.0-2.2-2.4, prefer 1.5" pipes.

Larger diameter pipes simply kill the low & mid-range power without a payback on top (above 6.5K) and they generate uneven A/F ratios which can be observed in the AFR plots. The torque curve mirrors the A/F curve so as mixtures vary, so does torque.

IMHO, larger but shorter primaries do not pay dividends.

There is a possibility that some kind of stepped header might work pretty well too, but that would require some detailed and lengthy dyno tests to prove that.
__________________
Steve Weiner
Rennsport Systems
Portland Oregon
(503) 244-0990
porsche@rennsportsystems.com
www.rennsportsystems.com
Old 07-01-2006, 02:02 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #13 (permalink)
Registered
 
Join Date: Mar 2005
Posts: 743
Great advice, Steve.

I will pm re headers.

Kind regards
David

Old 07-02-2006, 12:43 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #14 (permalink)
Reply


 


All times are GMT -8. The time now is 10:25 AM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2025, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2025 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.