[DeTomaso] Dynomation as a Dyno Lie Detector

j g notstock at yahoo.com
Mon May 17 13:36:55 EDT 2010


increasing compresion ratio will increase Hp over a wider rpm range , going from 9.5 to 1 to 13.5 to 1 on especially small displacement motors brings the torque up quicker in the rpm range and ends up producing a much broader torque curve than lower compressinon ratios .
The issue with dynomation  program (i own both older as well as current versions) is that the effect of improved octane rating and optimum spark needs to be adjusted to be able to use the higher compression ration effectively .  in a 3 liter ford motor  for my race car the increased compression was worth 32 hp @ 7200 rpm and 24 hp at 3200 rpm  over the lower 9.5 to 1. Remember it is effectively the area under the HP curve over the rpm that you are geared for that accelerates a car . 
 
jg  

--- On Mon, 5/17/10, Art Stephens <artstephens at verizon.net> wrote:


From: Art Stephens <artstephens at verizon.net>
Subject: Re: [DeTomaso] Dynomation as a Dyno Lie Detector
To: "Will Demelo" <wdemelo at cogeco.ca>, "Daniel C Jones" <daniel.c.jones2 at gmail.com>, "Pantera REALBIG forum" <detomaso at realbig.com>
Date: Monday, May 17, 2010, 11:28 AM


Will,
I remember when I first learned about the very minimal gain in horsepower by 
increasing the compression ratio,  I was amazed!  It does seem that the risk 
of detonation would not normally be worth the small performance advantage 
for many of us.

Art



----- Original Message ----- 
From: "Will Demelo" <wdemelo at cogeco.ca>
To: "Daniel C Jones" <daniel.c.jones2 at gmail.com>; "Pantera REALBIG forum" 
<detomaso at realbig.com>
Sent: Saturday, May 15, 2010 5:15 PM
Subject: Re: [DeTomaso] Dynomation as a Dyno Lie Detector


> Increasing the compression from 9.8:1 to 11:1 only made 6 or 7 more
> horsepower? I would have thought that more compression would have made 
> more
> power. Why would someone take the chance on detonation for only 7 more hp?
> Will
> ----- Original Message ----- 
> From: "Daniel C Jones" <daniel.c.jones2 at gmail.com>
> To: "Pantera REALBIG forum" <detomaso at realbig.com>
> Sent: Saturday, May 15, 2010 6:37 PM
> Subject: [DeTomaso] Dynomation as a Dyno Lie Detector
>
>
>> That suspicious Powerblock 351C buildup has re-surfaced in March 2010
>> issue of
>> Muscle Car Review magazine in an article entitled "Cleveland Hall of
>> Fame".  The
>> article has a picture of the "finished beast" without distributor, water
>> pump,
>> balancer, thermostat housing, etc. and claims it was dyno'd at 466 HP and
>> 471
>> ft-lbs of torque but no RPM values are provided.  It also claims a
>> compression
>> ratio of 9.8:1, though the Edelbrock Performer RPM 351C-2V cylinder heads
>> are
>> nominally 60 cc's and Keith Black KB177 flat top hypereutectic pistons
>> are used.
>> Those pistons have a 1.67" compression height and valve notches of 2 cc's
>> and
>> are listed by Keith Black as providing 11.07:1 compression ratio with
>> 62 cc heads.
>> I ran it through a compression calculator that I wrote, assuming 60 cc
>> chambers
>> and a Fel Pro headgasket of 0.041" compressed thickness and got an 11.1:1
>> compression ratio.  Not even close to 9.8:1.
>>
>> The article states the camshaft was a Comp Cams part number 32-000-5 
>> which
>> is
>> a generic core part number.  I believe that to be a typo and the part
>> number is
>> actually 32-600-5 which is the smallest 351C Thumpr cam:
>>
>> http://www.compcams.com/Cam_Specs/CamDetails.aspx?csid=1477&sb=2
>> Grind Number 279TH7
>> Thumpr Series hydraulic flat tappet, high performance street, stock
>> converter ok,
>> best with 2000+ converter and gears, choppy/thumping idle, 2000-5800 RPM
>> range
>> 278/296 degrees advertised duration
>> 226/241 degree @ 0.050"
>> 107 degrees LSA, installed on an intake centerline of 102 degrees
>> 0.506"/0.493" valve lift
>> 0.300"/0.291" lobe lift (appears to be a typo on the lobe lift or
>> assuming short
>> than 1.7 rocker ratio)
>>
>> 0.006" valve timing is given as:
>>  int open  39 BTDC
>>  int close 67 ABDC
>>  exh open  80 BBDC
>>  exh close 45 ATDC
>>
>> The specs listed in the article are hydraulic flat tappet with:
>>
>> 278/296 degrees adv. dur., 0.491"/0.476", 107 LSA
>>
>> but the lift assumes the 1.7:1 rocker ratio of the Comp Cams Magnum
>> roller rockers
>> used in the build.  Still, the lift numbers don't quite match up to
>> either the lobe
>> or valve lifts from the Comp Cams card.  If you assume the valve lift
>> in the Comp
>> card is with 1.73:1 rocker ratio, the lift with 1.7:1 would be
>> 0.497"/0.484".  If
>> the lobe lift is correct on the Comp cam card, the lift would be
>> 0.510"/0.495".
>> Let's be generous and use the largest lift and assume cam specs of:
>>
>> 278/296 degrees adv. dur., 0.510"/0.495", 107 LSA
>>
>> Edelbrock cylinder heads 2.05" 1.60"
>>
>> http://www.edelbrock.com/automotive_new/mc/cylheads/ford/cle_perf_rpm.shtml
>>
>> Lift     Int    Exh
>> 0.100  058 054
>> 0.200  120 105
>> 0.300  180 138
>> 0.400  227 151
>> 0.500  260 161
>> 0.600  265 165
>>
>> Flow numbers as tested on Edelbrock's SuperFlo SF-1020 flow bench.
>>
>> Inputting everything optimistically and using Edelbrock claimed flow data
>> with open headers and 9.8:1 compression ratio:
>>
>> 422 HP @ 5000
>> 470 HP @ 4000
>>
>> Increasing compression to 11:1:
>>
>> 429 HP @ 5000
>> 476 ft-lbs @ 4000
>>
>> With TMeyer independent flow bench data on Edelbrock 2V heads and 9.8:1:
>> 416 HP @ 5000
>> 472 ft-lbs @ 4000
>>
>> With cylinder head flow from Cleveland Confidential magazine article:
>> 419 HP @ 5000
>> 471 ft-lbs @ 4000
>>
>> In my experience, when fed accurate data (actual cam timing specs, flow
>> bench
>> data from Dave's conservative bench, minimum/maximum port areas, etc.),
>> Dynomation has been close on the HP but optimistic by 20 to 30 ft-lbs
>> on torque.
>> The above simulation is likely optimistic since the minimum port sizes 
>> are
>> assumed to be the same as an unported iron 2V head.  The simulation is
>> quite
>> sensitive to the minimum intake port area.  A slight increase in that can
>> drop
>> the HP prediction by 10 HP.  The simulation is less sensitive to larger
>> minimum
>> exhaust areas (at least for a relatively large port engine like a
>> 351C).  In any
>> case, I'll buy the Power Block engine made over 400 HP (assuming it was
>> ever
>> dyno'd which I see no evidence of) but not the claimed 466 HP.
>>
>> As a point of reference, Edelbrock claims:
>>
>> 456 HP @ 6000 RPM
>> 445 ft-lbs @ 4500 RPM
>>
>> for a 4.04" bore by 3.7" stroke, 9.75:1, Cleveland with RPM Air Gap 
>> intake
>> and flat tappet cam with specs:
>>
>> 312/322 degrees advertised duration
>> 234/244 degree @ 0.050"
>> 112 degrees LSA, installed on an intake centerline of 107 degrees
>> 0.571"/0.589" valve lift
>> 93 degrees overlap (seat)
>> 0.050" valve timing is given as:
>>  int open  10 BTDC
>>  int close 44 ABDC
>>  exh open  59 BBDC
>>  exh close 5 ATDC
>>
>> With the above entered into Dynomation, along with Edelbrock's claimed
>> flow bench data and 750 CFM of carb flow, the predicition is:
>>
>> 434 HP @ 5000 RPM
>> 460 ft-lbs @ 4600 RPM
>>
>> With 800 CFM of carb flow, that increases to:
>>
>> 444 HP @ 5600 RPM
>> 463 ft-lbs @ 4600 RPM
>>
>> for the headers assumed.  The Edelbrock numbers are much more believable.
>> The Power Block build reads like fiction.
>>
>> Dan Jones
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