This is the latest installment of my SR vs MR saga. These results will/may be considered by some to be an apples vs oranges comparison, however I think there's still some useful infomation in here, but it's only my personal view.

Last October I ran my SR/219 combo on a Dynojet at Altered Atmosphere Motorsports in Gaithersburg, Md. along with a number of the local CF members. By the end of that day I had made 6 pulls, played with the timing & FP and recorded a best of ~415 RWHP @ ~5-5500 RPM & ~499# RWTQ @ ~4-4400 RPM.

This past Saturday I pulled it again 5 times on a Dynojet with a few of the same Corvette Forum members in Damascus, Md. at Main St. Speed & Sound. The only engine change I've made is the removal of the SR and installation of the MR, same injector size, TB, cam, timing, chip.....etc. As for the drivetrain, in the spring of 2003 I removed the 700R4/D44 and replaced them with a TH350/9" due to continual breakage last year. This Saturdays dyno results where that the RWTQ & RWHP shifted higher in the RPM range as expected due to the MRs shorter runner lenght. But strangely, this time the TQ increased and the HP dropped a tad. Played with the FP & timing after the baseline pull to tweak a few more #s/ponies out of it. New results are 525 RWTQ and 401 RWHP @ a few hundred RPM higher than before, however, both curves appear to have flattened out & the peak lasted longer.

I'm not relying solely on dyno numbers at all in this comparison because it was a different location, weather, converter locked(?) vs not locked, etc. not really a controlled enviromental test. Both intakes really work well, the SR on a stock or mild engine at low RPMs on the street is a tough combo to beat. Big engine @ higher RPMs I think the MR breaths a little deeper with no noticeable loss down low.

Since the intake change I have continued to run the car each weekend and can tell you the torque didn't go away and the pull at upper RPM is stronger, hence the new best 60', ET & MPH in my signature. True the air quality improved and maybe the SR would have improved also, but I still don't think it would have picked up this much.

Considering this is still a pump gas capable engine with only a 219 cam I wonder what it would do with more duration & lift? Maybe add a dash of compression over the winter?

Well it's a nice day outside, I think I'll get started on installing my NEW cam, enjoy,
Dave :D :thumbs:

 

Great test…the cam test will be interesting too. Nice work !
:thumbs:

 

:iagree:

Looking forward to the results of the new Cam.

 

Very interesting, I am surprised the cam still works os well on a big cube, 215CC head engine!

 

Dave,

Good report. No idea what the DAs were for those days to give a little more insight to what was going on? Did you get some AFR numbers? IM me when you get some time!

Jesse :thumbs:

 

i really find this very interesting. you dont by chance have any pictures of the old dyno curve and the new one? And for the rest of us who dont know exactly what you got under hood, what kind of heads, bore & stroke, and exhaust are we looking at?

i like the 60' time btw. very nice :D

 

FWIW: The Turbo 350 will be a little more efficient than the 700 and the 9" will be considerably LESS efficient than the D44... That could account for a little of the difference you're seeing here. But the obvious conclusion here is that the SR is probably optimized for the LPE219 combination...More cam and the MR will show where its potential is. Good test...
-Jeb

 

Jeb,

Not sure I fully follow this statement. :confused: I would think that the 9" being more of a "direct" link in terms of the axles etc, that there would be much less loss than opposed to our IRS systems that have not 2 U-joints but 6 joints. The driveshaft ones are pretty much straight on, but the 1/2 shaft u-joints are not always that case. More angles than straight line. I would think our D44s would be less efficient than the convential rear setups.

Mayeb I am missing something. I regard your opinion highly and would like to hear your thoughts on this.

Last night Corky and I were talking about this exact thing on the phone.

-Jeb[/QUOTE] :lurk: :thumbs:


[Modified by ski_dwn_it, 1:56 PM 10/20/2003]

 

just a guess, but maybe the smaller ring and pinion and also i'm sure the (short)alum half shafts take alot less power to rotate than a steel axel in a 9".

this is just my guess though, Jeb will enlighten us soon.

Oh and off the subject but have you run that modified intake yet ?

 

Bingo... The large, heavy 9" Ford causes a greater parasitic loss than does the smaller Dana 44... The 9" has always been known as a power robber but due to it's strength (and wonderful "third member" layout) is popular. The D44 has a much smaller ring gear and pinion, lighter "axles", and simply more efficient layout. The 9" has a different tooth engagement as well and this causes loss, too... The 12 bolt, D44, 8.8" Ford, 10-bolt GM (the good 8.5" one), and the Dana 60 are all more efficient rears than the 9" and will sap less power. Kinda like a Turbo 350 vs. a Turbo 400...The Turbo 400 is heavier with a less efficient planetary than the TH350 and will use more power. But it will take more abuse. The only exception here is the Dana 60...It's every bit as strout as a 9" (witness the 35 spline axles) and IS more efficient but it's also physically heavier by about 35 lbs...
-Jeb

 

Jeb,

Ok that makes sense, but what about the u-joints not actually being in a straight line. Sorta like torque on a ratchet when using a knuck adapter. You will get most torque, with everythingi in a straight line. Each angle off that reduces the amount of torque. Wouldn't the same apply here, and ultimately offset the advantages of the weight?

Strange when you start looking at each thing, all the different sceneros that play into make the most of your power. It'll drive you nuts!

Intake test is still scheduled! Indians are waiting patiently! :D :thumbs:

 

I believe the loss in the 9" comes from the pinion being located lower on the ring gear in relation to the axle centerline compaired to 12 bolts, etc.
:confused:
BTW, new cam is in the engine! I got bored this afternoon, so I didn't start until after 1PM :D . I have to go out of town for a few days, so hopefully I can finish up and run Sunday.

Dave :chevy


[Modified by hookedup, 7:32 PM 10/20/2003]

 

And what may we ask is the new cam pecs :confused: :confused: :confused:

The suspense is killing me!

 

Let's see here Hmmmm



HOOKEDUP! ;) I HAVE TO SEE THIS CAR RUN WITH MY OWN EYES!!!!!! :smash:


[Modified by Jay 383, 8:26 PM 10/20/2003]

 

jeb you are right about the 9 inch sucking up more power but transfering power through those half shafts moving at all different angles going down a track has to account for a lot hooked up picked up an easy 4 tenths in the qtr with the 9 inch 4 link and turbo 350 setup and i would guess most of that is directly transfered from the straght axle compared to our pretzle rear setup
what are your thoughts :cheers:

 

Now there's a curveball....more TQ and less HP with the MR vs SR...go figure...LOL!!!

It seems to me that regardless of the efficiency of the rear, the th350/4link lowered your ET a bunch. I guess the ratios of the th350 are better suited to drag racing than the 700R.

Whatever it is, it's working and i'm taking notes :yesnod:

New cam results should be interesting!!!!!!!

 

ralph i have so little respect for rear wheel dynos its pathetic unless you are the for the same day same weather and so on its just like taking the car to the track you can vary day to day let on week to week look at jesses his first dyno was right after he got the car togather and dynoed 437 rwhp then gos back to the dyno again two months latter and gets 380 rwhp thats like 60 hp that is crazy then look at my car did 379 rwhp and runs the times it runs they are good to tune it on for one day and one day only if you have to go back the next day anything can happen :cheers:


[Modified by CORKVETTE1, 9:54 PM 10/20/2003]

 

Cork, Yeah I agree with you that they vary quite a bit, granted the air was terrible the second time around, 3000+ DA (guy had a weather station, his dad brought over)...and it made 399, not 380 the second time around, but that really is not the point.

THey almost need to be corrected to SAE, then it puts them a little closer, but there will still be variations. Just no getting around it. :iagree:

 

HOLD UP> when is it scheduled for? i need to know :D i really am waiting this one anxiously :yesnod:

 

Larry,
The cam is a custom grind from Comp Cams that we collaborated on the specs, quite a bit bigger than the 219 I took out :D closer to what Corky & Jesse are running.

Dave :flag