My SR upper should finally be back at home from the polishers this Saturday. Before I install it I was planning on being a guinea pig (as discussed in a previous thread long ago) and doing a before and after dyno run. I also want to dyno it to see if I need to change my shift points at all.

I've never been inclined to dyno my car before and would like some opinions as to what rpm I should tell the operator to finish the run on. I want to do a fair comparison between the intakes without breaking the car. I was thinking 5000-5200rpm with the stock runners and possibly 5500rpm after I put the box on. I never rev my car this high on the street deliberately but it has seen those revs more than once on the track and once when i missed a gear :eek:. Will I hurt the valvesprings or something else if I rev a stock motor that hard for dyno purposes?

I'm thinking 5200 for the stock runners because I really think power will drop off by that point - this may well be the same with the SR upper but I don't know for sure - hence the higher rpm limit.

I know my stock cam should give up on making power at about 4500rpm but am wondering if I should spin it higher just to see if the SR makes much difference at higher rpm without the cam.

Anything I might have overlooked?

Thanks in advance.


[Modified by Red 90 L98 Coupe, 7:17 PM 6/20/2002]

 

Isn't the purpose of the dyno besides knowing your HP is to -
Discover your best RPM/torque/power point.

Why would you push your engine so hard if you can see the HP curve at 5000 o r 5200. You can easily see if you have more power or you are on the downward leap.

Do a few runs to see how your HP/Torque peaks and use this optimal RPM.

I found that the SR intake increased my optimal RPM from 4400-4500 to 4800.

Use the Dyno to tune and learn about your engine and its power curve.

Good Luck and have fun!!!! :cheers:

 

I do believe I've been putting entirely too much thought into this. :yesnod:

Just to explain my thinking, I was thinking of spinning it so hard to see if there is a distinct dropoff in hp/tq around 5000revs with the normal runnners and SR base vs the SR base and upper SR plenum.

 

i use my 85 vette for my dyno mule..spinnin it much past 5000 is a waste of time and fuel,however mine is stock,try runnin the sr up a couple hundred more rpms,that should give you enough info. since may 1st,i have more dyno miles on the car than road miles...i need to get a life! :D

 

I used to run my car up to 5500 all the time with no problems. I realize that the power drops off after about 4700 with the stock setup, but it never hurt anything. With the stock bottom and the new setup I shift at about 5600-5800, but it has seen 6400 with no problem at all. On the dyno pulls the HP is a constant increase... just not to much towards the end, so a shift of about 5600-5800 is best.

All in all, engines are going to vary a bit, but you are not going to hurt the engine, provided it is in good working condition. A 350 takes a pretty hard beating before breaking.

 

1985z51 - Do you work with access to a dyno? - dyno runs ain't that cheap (relatively speaking) over here....

ski_dwn_it, I hear ya about these things taking a beating. :D If/when mine finally gives that will give me an excuse - er, I meant reason to build a motor. ;) :jester


[Modified by Red 90 L98 Coupe, 2:17 AM 6/21/2002]

 

Make sure when you make your runs to start at the same coolant temps, and the same speed (I'd run it from a rolling 15-20mph vs. a dead stop). It's the only way to get consistant repeatable numbers.

 

Just curious, one of the places I spoke to about doing a power run on a dyno said they were busy tuning chips (they are) and that they could do a power run for me between setting up cars. All I had to do was leave my car with them and they would call me when they finished with it. Because they were so busy and they didn't know how long it could take, I asked if I could wait (didn't care how long) and watch them when they did it and they said I had to drop the car off and leave it with them. :eek:

Somehow I had a huge problem with handing my Vette over to them and trusting that they would do the right thing while I was away. I thanked the guy or his time and hung up.

Am I overly protective or was this shop nuts for expecting me to leave my car with them?

I'm waiting till Tuesday (or later) now so I can do the dyno run through a friend of mine who has a friend that runs a dyno.

 

The way we did mine was to conduct all the runs in 4th gear since it's a 1:1 ratio and start from whatever rpm you want. I usually do about 2500rpm and took mine to about 5200. You'll see your power drop off before the 5000rpm mark but I'd take it to at least 5000rpm on the before test. If it were me I'd take it to 5200rpm on the runs before the superam, then do them to 5500 after and compare. I also do 3 runs real quick, back to back to back, to get a good idea since they can vary a bit. Do 3 runs then let it rest/cool and do more if you want to. I'll be very very interested in the results so please let us know. :yesnod:

 

my dyno is in my garage...every night i pull the vette on it ..its only a 2 1/2 car garage so its pretty full. its been the neatest tool ive ever bought,you will learn more about your cars capabilities in the few minutes it takes to run than you would in hours of track time...like i say whats your time worth? what does dyno time really cost over there? i use mine for my own stuff..but it might be worthwhile to rent it out. i dont even know what anyone around here charges

 

What is redline on the car? I believe it is 5500 rpm (my 91 was).

If I were doing it I would start as low as I could and run it completely to redline. Definitely note all parameters such as temp, humidity, pressure altitude if they have it, coolant temperature, oil temp, etc. This way you can refer back to them if you ever do another test. Better to know the whole story before you start changing things-this is a good baseline.

Unless your engine is only last legs...going to redline certainly won't hurt it...matter of fact you may see bits of carbon come out of the tailpipes and might even pick up some power on the second run due to this.

I definitely drive my own car and watch them to the hook up, etc. Lots of different cars out there and they operators can make mistakes...in other words wouldn't bother with them if they won't let you be there when the car is tested.

My example on my 96 LT4: they used a Mustang 1750 dyno and I started runs at 1000 rpm (mine is a stick) and didn't stop until I hit the fuel cut off (6400)-this is 100 rpm past redline. My car has 75,000 miles on it and I don't have any doubts that it will take it:) On the subsequent tests I did nearly the same thing...this gives be excellent back to back results that are as useful as they can be.

Besides it is unreal sitting in your car while it screams and it isn't going anywhere-no wind noise to cover the awesome sound!

:D

 

Lots of great feedback here. :yesnod: :cheers:

I think it will be 5200rpm (or 5500rpm) before SR and 5500rpm after SR.

I have to say the SR looks sweeet all polished up - it is sitting inside on the lounge room table assembled because I don't have anywhere else to set it down right down right now and I keep going in there to look at it...:crazy: I think I need to get a life.

I will be sure to post the results here. The main reason I'm doing the before is so I have a comparison to report back to you guys here - otherwise I could probably get away with just an after run to check the shift points and then a follow up trip to the dragstrip.

I'm thinking if I am able I will see if I can sit in the car and watch the diacom while the runs are being done, won't be able to record through diacom though because even though I paid for Diacom "plus" it looks like I got the plain old "normal" diacom. Thanks MAD.
:rolleyes: (Didn't bother following up on if I could get it exchanged because it was so long between my purchase and working the problem out... :rolleyes:)

No way I will take it somewhere if I can't be there while they run the car. I would like to be outside the car on one pull if I could so I can hear what my mufflers sound like from outside the car. :crazy: But would rather watch what is going on incase I might learn something... I will be surprised if I get carbon out of the tailpipes with my driving habits though. ;)

I have a few more calls to make tomorrow about costs and where etc although I will likely do it via my friends contact - I'll report back on that side of things then.


[Modified by Red 90 L98 Coupe, 1:20 AM 6/24/2002]


[Modified by Red 90 L98 Coupe, 3:07 AM 6/24/2002]

 

Shhot an email to Craig Marcho about the diacom. He may be able to help you out on getting the
+plus part

 

In S. Florida (Dania/Ft Laud) Breathless Performance (a forum sponsor), charges $75 for 3 pulls. I've also been to a few car show/swap meets where the prices were similar ($50-60 for 2 pulls)

Someday my project will be done and I'll get to use this cool tool :yesnod:

Dr.

 

What kind of dyno do you have? Even a portable dyno is pretty big, expensive too. I couldn't see buying a dyno for occasional use.

 

I spin mine up to 7,200

I'd run it up until you hit redline. You're not going to have any wind drag, so it doesn't take that long or that much effort.

 

i have a mustang md250..i inherited it because someone wasnt able to repay money they owed me. it was either take the dyno as payment or lose everything. he wasnt makin money with it and so far neither am i. i will say that its a heckuva lotta fun. had a big block 55 chevy on the other day..565 ft-lbs of torque at 4200 rpm..WOW best runnin corvette so far is mine...207 rwhp at 3800. id like to use it more but so far there hasnt been alot of interest..one thing i think thats funny,engine builders that dont have one wont use one...evidently their butt dyno works better than my mustang. there has been one car that ive given alot of attention..its an injected 5.0 mustang(sorry..flamesuit would be on but its hot here today!)over the last month we've gone from 262 rwhp to 312 rwhp..a real nice improvement for the time invested! :)

 

You could make a good buck off it if you advertised doing dyno pulls for people. People eat it up, they just need to know it's available!!

 

i agree about the advertising..my ad comes out next tuesday. today i ran a 2001 firebird firehawk,gm says 327hp at the flywheel..81 degrees and almost 60% humidity this thing makes 300rwhp..you do the math! i have discovered that there are lots of people willing to spend money on hard parts,but wont spend a buck to test! oh well..if it doesnt pan out i could use it for a bbq pit :D

 

my dyno sucked :mad have a good day :lol: