skinny z

I'm off to the chassis dyno today.
12.77 @ 105 is the best run to date.
Details are in my signature.
Any guesses as to actual horsepower/torque numbers?
For the record I predict less than 300 rwhp however I do anticipate a broad torque curve. Perhaps 350ft/lbs from about 2500 to 5000 rpm.

AlkyIROC

Can't guess at a HP without knowing the race weight. A light vehicle needs less HP to go the same speed as a heavy vehicle.

skinny z

Very true. I should have listed the race weight. The specs are in my sig.
For the record the vehicle weighs 3700lbs w/driver. ( Four corner electrionic scales ).
I should qualify my guess by saying less than 300 RWHP however as far a torque goes, I'm guessing actual crank values ( of 350 lbs/ft based on a 20% drivetrain loss).

raptor80dad

How did you do?

My best is 12.76@ 105.5 1.75 60"

3180 w/driver
250rwhp
270ft/lb

TH350
3:73 posi

Your guesstimate should be close.

AlkyIROC

Since it's a guess based on your best performance, the numbers I come up with are 330-350 HP. That's how much power it took to move that much weight to 105 MPH in the 1/4 mile on that particular day. A dyno factor needs to take into account the air conditions so dyno HP will probably be greater. Dyno HP will always be corrected to sea level conditions so an engine dynoed in Denver will have the same results if dynoed in Florida even though in Denver it's making a lot less HP.

It's unlikely that you'll ever see the dyno HP at the track unless you happen to be at the track with mineshaft air.

Come and race in Calgary, you probably won't get out of the 13's.

Orr89RocZ

iTrader: (20)

i went 103.8 on the best day possible here in PA with a 3450lb raceweight and 254/315 whp/wtq. I would figure you are in the 280-290 range. My 3600 ish lb LS1 auto car goes 104 in decent air with 2.73 gear/stock converter, bone stock motor. figured 280-290 whp. Most M6 cars dyno around 300-310 and run 106-107

IHI

iTrader: (1)

I would venture to say...who gives a #$^%?? Is there a place that gives out cookies to dyno number performance? Take whatever they give ya and throw it in the trash since nobody races a dyno...engine or chasis, let the time slip be your true evidence with what your doing...anything else is a joke.

are you just going over to tune the car? or puffy chest with numbers LOL!! Friend on mine on another forum chasis dynoed and would'nt post numbers because he was trying to track down a problem and he knew how guys would react...for the record he had a 10.80 car and the "dyno" only showed him putting out 280hp LOL!! Stories like this going other other way are much worse...2 of my freinds go to chicago to some "big time shop that works on high end cars" and took their turbo and the other s/c with nirous car over there for tuning. got texted laid down 750hp tot he tire and the other was just over 800hp to the tire....guess what? neither of them POS cars ever got out of the 11's. I had my junk on one years ago, buddy and i told the shop owner he was nuts and the dyno was wrong...they did'nt want to hear it, they're too pumped up over the ridiculous numbers my 388 put down but in real life was nooo where near that...i'da been running single digits if i would'nt have ripped the car in half according to dyno numbers.

point being, unless your trying to tune, save your money..brining up chasis dyno numbers to your clueless buddies will make ya sound impressive, bring them up around actual car guys that know WTF they're talking about, and you'll go home with your tail between your legs.

skinny z

I give a #$^%.
That's why I went.
I'm not about to puff out my chest or wither away regardless of what the numbers indicate.
I'm interested in the numbers. Both from the drag strip and the dyno.
Did I learn anything? Most definitley. I learned that my tune is about as spot on as I could achieve.
While I'm not thrilled with the dyno results, it falls in line with real my world performance and the theoretical calculators we all use.
It was a very interesting experience.
Do get me wrong IHI. I appreciate what your saying. However for me it was money well spent even if you just consider the entertainment value.

skinny z

Incidentaly, I do bring up the numbers to actual car guys and they find the data interesting.
Just a they find the time slip numbers interesting.
So do you from the sounds of things. At the very least it makes for some fun dialouge!

IHI

iTrader: (1)

Yep, all i can think about is if my old 388 made as much power as that POS chasis dyno said, and my 427sb is making as much as it does...i seriously need to consider specing and selling my sbc's to peterbilt, caterpillar, etc...because they're all monsters on the rollers!!!! Just like my power adder freinds that lay down big numbers on the drums but their junk wont fall out of a tree at the race track.

Chasis dyno's are like bang'n a fat girl..ya gotta do it once so you can say you did as a life story, but dont go into detail about what you just went through....nobody really cares LOL!!

If you learned your tune is spot on that's the important thing, and the only thing to really use ANY dyno for, trying to brag on numbers=wetarded

DIGGLER

iTrader: (1)

yup, its always interesting to hear someone talking about their nearly stock engine laying down 500+ ft.lbs.
my next question after they tell me that is what kind of converter did you put in it? (converter flash)

Orr89RocZ

iTrader: (20)

I used the dyno to verify my tune and picked up alot of hp/tq on the dyno that day. Went back to the track with the new found knowledge of my powerband and increased power and picked up 2mph and about .15 ET on same 60 foots.

Dynos are a tuning tool but since they all vary greatly its hard to trust the numbers

That being said I hope to put my turbo car onthe dyno just for the bragging rights and look at the curve but i dont expect big numbers..but the car will just about run 9's which is all that counts to me

skinny z

You want to know what's really cool?
A lot of respected members of this forum have chimed in with their opinions.
If that's all I get out this, then it's time well spent.
For the record, peak rwhp of 282.
Peak torque, 283.
Just like they said it would.

skinny z

Hey Stephen,
I know that's true.
My best track time had an density altitude of 250' BELOW sea level. ( mine shaft air )
If I apply the conditions of the day ( 6*C, 102 kpa, 45% hmd ) and allow for your 3500' altitude, I manage to scrape out a 13.25 @ 102!
My intention is to get to Edmonton this summer and race a little there. That should be interesting.

JesasaurusRex

iTrader: (3)

IHI pretty much covered it

leave the dynos to the LS1 guys

sh*t's pretty useless

IHI

iTrader: (1)

Well, the "bragging" aspect that so many clueless use them for IS useless since it dont matter what the computer says it should do compared to what the car REALLY does. Tuning wise, be it pump or rollers alot can be learned quickly since the actual data is right there in your face. There are certain things that can be tuned for the better in real life vs hypothetical too, but if any dyno is used as a tuning tool only and not a platform to try and base bragging rights then it's time and money well spent. Before i started engine dynoing it'd take me a few weekends, countless passes trying different things since i needed back to back passes to back eachother up to show a good change or a bad change. Now for the past 5 years we engine dyno everything, you hit the mark within 4 pulls and it's done, ready to drop in a go. IF i want to experiement with jetting i can...but timing will always be what it is, when optimized so it basically only leaves fuel and air to mess with, which both take time on a track.

Sounds like Skinny has the facts straight on this matter, i just feared the worst since i've read soo many ridiculous "chasis dyno" threads over the years i expected the worst LOL!!

skinny z

Thanks for that IHI.
It's certainly not a bragging thing.
Look at my numbers and know that's true. Although I predicted LESS than 300 rwhp, I was hoping for more. However, knowing what I know from my time slips, I knew it wasn't going to be the case.
I get more value out of my dyno time with every post.

JesasaurusRex

iTrader: (3)

i'm sure there are SOME benefits to a dyno, however i still believe them to be minimal. I've NEVER had my car on a dyno...okay that's a lie...ive had my car on a dyno once, and it died on it but that's another story. I just don't think a dyno simulates real world enough to be that useful. G-Forces, actual load, etc etc. If the secondary jets go lean leaving the line the dyno will never tell you...etc etc. Read plugs, tune for mph, dynos are over rated imo. Grain of salt for everything at the same time

skinny z

[QUOTE=JesasaurusRex;4338234]i'm sure there are SOME benefits to a dyno,QUOTE]

That is also true.
Even if it's for a 2nd opinion.

IHI

iTrader: (1)

Yes and no...nothing will mimic real life like going down an actual race track when G force is affecting fuel flow throughout the entire fuel system fromt eh tank to the carb, we found out engine dynoing my stuff sitting idle on a stand i would get air in the oil system mainly because G force was'nt pulling the oil back towards the pump pick up...but i can tell you for a fact 4 pulls on a chasis or a wheel dyno will get you closer than 20 trips down the track because when all you have is time on a track there are multiple factors all playing into and tainting possible findings, dynoing is a controlled test since nothing changes.

Tuning at the track:
it takes 2 passes to back up 1 change to be sure it was'nt a fluke, to make sure it was a change in the right direction because you have to wonder:
did the air change somewhere going down the track
did the carb ingest colder/warmer air at some point going down the track
was there a cross wind that may have hit the car this time vs that time and at possible different spots on the track while the car is accelerating
did you hit the EXACT shift point each gear change
did you stage in the EXACT same spot
did you bring the rpms up to the exact same spot or did the ignition 2 step vary by 1-200 rpm if using a 2 step (it happens)
and if you do everything the same, it still takes 2 passes to back up what you changed...so now factor in jetting, going up 2 jets you go faster, you go up 2 more and slow down, you step down 1 jet and pick back up...well there alone is 6 pass....remember on track gains are usually in the .0X of a SECOND...anything and EVERYTHING can and will affect the car to mask that .0X your tuning for.

in 4 pulls on a engine dyno my engine was 100% tuned to the max for that session and it took all of 20 minutes, the rest of the time was all experimental. Initally you find the timing, 34* for me was optimal...35* i lost 15hp, 33* i lost 21 hp...there is absoltely NO WAY you will see 15-20hp on the race track on modified engines...stock engines you will, but where we're at, 15-20 is'nt squat....and this is where the dyno sessions shine you can see and record that 5hp here, that 15 hp there and when you all said and done i know with a few of my engines in 4 pulls we've increased 70hp over base pull....there is no way you'll do that just dropping a grinder between the fenders and heading to the track...hence the open test and tune sessions for guys that think spending a few dollars to dyno is a waste of time...but they'll drop tow money going to/home from the track, they'll spend how much in fuel making passes, spend how much time tinkering under the hood, waste how much rubber in tires making passes testing and chasing the tuning they're doing....that's why for me after we dynoed an engine years ago i seen it was a no brainer...when i put the engine in the car it's 95% there...and to be honest, i'm okay with 95% and not opening the hood ever again.

I'm alot more privey to engine dyno's over chasis dyno's and i know other's favor chasis dyno's over engine dyno's since it's taking everything into play..but since i'm not out trying to break speed records with my tank, i dont care about any little spikes that may occur in the tune if the drivetrain makes a difference or not..all i care is that it runs good and repeats. Once you set aside some coin to engine dyno, the picture will become crystal clear, i will never not dyno anything going in my car ever again, there's just far to many benefits that outweigh the few not even argueable points as to why not to do it.

JesasaurusRex

iTrader: (3)

A dyno will get you closer to what? It's still not real world. When i hit the strip i'm not "well my sh*t went 153 last week, whys it only going 151 this week with the same tune?" You obviously have to tune to the base line of the day (first pass of the day in my world). That being said the weather and conditions are always changing and even if you make a pass 30 minutes after the first it's still a possibility that you're going the wrong way. However fact of the matter is you're still making ajustments depending on how the cars working and depending on the time frame you're making back to back passes i'd say they're more credible than dyno pulls...especially if we're talking motor and not chassis. That being said, i'm trying to get down the 1320 as fast as i can, i really don't give a fawk about a number i can post on a youtube video about how much horse power my trash can make...

ZONES89RS

iTrader: (2)

Dynos are for tuning... Nothing more. Some like to use them to brag i guess.


My 95 Z with a SBC vortec carbed 357 made 311 RWHP on a mustang dyno, felt slower than my stock L98 with a carb swap in my 89, but it had 4.10s.

Never got it to the 1/4, but it did 84 MPH in the 1/8th with the T56 and stock 3.23 hears in the 95.

Orr89RocZ

iTrader: (20)

Well i did see a gain in et and mph at the track after my dyno tuning session. I showed 15whp peak but that was on a heat soaked motor so the final pull may have showed 20-25whp or more overall. This was on a mid 11 second 383.
But the biggest gain I was able to see was in the mid range... the torque went up 30 lbft because when street tuning you need to do a strong pull in your third gear with converter locked up (700r4) to see broad rpm range and 3rd usually will give most load on the engine... Well its hard to do a 50-120mph pull in public. With my twin turbo car now...its IMPOSSIBLE for me to try going 140+ mph just to tune my high rpms on the street. So to the dyno we go...along with the track test and tunes

A big factor in my case was this. If you dont lock the converter rpms flash by in a hurry and you can not read the wideband fast enough to know what your air fuel was. Datalog on the 165ecm did not have wideband recording like my twin turbo setup now (code $59). The dyno was able to record those numbers however and I was able to richen up my midrange as it was very lean. It showed stronger 330-1/8 mile times which lead to 2 tenths on the 1/4 and 2 mph overall in similar weather.. just weeks apart in mid summer

IHI

iTrader: (1)

Your missg the point Jesse, by your way of thinking your telling me your popping the hood before every drive you make in your car to "tune it" to optimum for the air that morning, probably going to pop the hood and check jetting after you eat lunch for optimum tune at that time of day, and then after supper change jetting because the air is different again to achieve optimum tune in the evening?? From what your saying that is exactly how i'm reading it since your trying to argue the point dyno's are worthless because they dont mean a thing in the real world because real world is different.....and honestly, who the helll other than heads up class cars actually open their hood and change crap on race day, 90% of this countries racing is bracket/shoe polish racing and only a fool messes with anything on race day.

Just like monday when you drove your car...your tune was'nt optimum because atmoshpere was completely different than last tuesday when you drove your car and changed jetting.....it's called compromise, we all do it...the only people changing engine stuff every pass are heads up racers, and even some of them dont touch a thing..they get it close and just run it....just like using a dyno..it gets you close, and it gets you close 10x's faster than trying to track tune a car, but I'm sure all the big guys like rehr morrisson, sunset, shafiroff, all the major car builders, etc....would agree with you, dyno's are junk, a waste of time, it'd be smarter to just put together some new engine combination and put it in some vehicle and test it on a piece of tarmac on their facility because that's "real world" and dyno's dont mean chit When in reality it's like this:

You build two engines identical, I come down and grab one and you have one..when i say go, you start installing your engine in your car and i'll take mine to the dyno and we'll see who's runs better faster and better overall. later that night or the next day you'll still be wrenching or taking it to the track, while i'm drinking a beverage cheering you on the from the fence with my engine fully optimized in 4 pulls/15 minutes....leaks are already checked for and corrected since it's on a engine stand more/less, any problems are easily correctable, i'm not wasting money having to pull the engine back out because i found out something was'nt right, etc...

someday you'll understand it, you will never ever have your engine 100% tuned for each second it's running...you get it close and live with it, same with tuning...the day your tuning at the track will be different 4 weeks later...but you live with it.


Orr....I was talking engine dyno when i was saying 15-20hp...if you picked up 20-25 at the wheel, that's the flywheel seeing a gain of 30hp or so...you will see that, 15-20hp could easily be chaulked upto a whisp of fresh air while making a pass, a different shift rpm you may have screwed up, etc...those little increases can easily hide from you because a person can just as easily write them off as something else since the race track is not a 100% controlled environment.

skinny z

With regards to tuning, several valid points have been brought up here.
It's definitely easier and faster to tune on a dyno, engine or chassis.
To be really competitve, especially on a race weekend, it will undoubtedly be necessary to tune at the track.
It IS really difficult to tune 50-100 mph on public roads.
Now that I have the correlation between actual time slips, computer simulation and dyno numbers, I feel confident that I can make a change and the results will be reflected accurately.
I'll give you a perfect example.
Some of you may have read about the exhaust terminator boxes that have been discussed here. It's very obvious how a decent exhaust system affects performance. I have LT headers, to a no cat back single 3" pipe to a very restrictive Flowmaster muffler.
From computer simulation, I can take all the specs of my car, including a poor exhaust and produce results that mimic almost precisely what I get at the track and as of a couple of days ago, on the dyno.
Stepping up to a more efficient exhaust I can see an improvement of about 30 chp on the computer. Keep in mind that my flowmaster muffler is probably limited to about 400cfm or so and essentially acts like a cork (sort of like the old banana up the tailpipe).
With that info, I'm pretty sure that I'll see improvements at the track when the new configuration is complete. I'm going to try my best to build a system that has "zero horsepower loss due to backpressure" ( quote Vizard ). I may try a little exhaust pressure wave tuning as well. What the chassis dyno demonstrated was that my little engine is about as tuned as it will get. About the only area for improvement is the exhaust. Although the track confirms that too, that are other variables when racing that affect performance. The dyno sort of isolates you from the track conditions.
Now before everyone goes off saying we don't race computers, remember that all those previously mentioned builders (rehr morrisson, shafiroff, etc.) build ALL their engines first with computer modeling. Same with cylinder heads and camshaft profiles.
So that being said, I'd say it's safe to say that we should be using all the tools available to us to make our cars as quick as they can be.

DIGGLER

iTrader: (1)

a dyno can get you where you need to be on the tune much more quickly than the track, as posted earlier. especially my car, being fuel injected. i can tune it on the dyno and get it dead nuts on the money, and once at the track it wont be that much different. however, the car going down the track will put a different load on the engine than the dyno would, so you may still have some tuning room.
a big selling point to the dyno is your ability to pinpoint problems such as weak valvesprings, burnt valve, wiped cam lobe, broken torque converter, or a bunch of other stuff that may be hard to notice by just running the car. there is a lot of guys shifting their car at 7400, even though their valves are floating by 6500. they dont know this, so they continue shifting at 7400 because thats where the cam supposedly makes power to. even though the engine is losing 100rwhp by that point. not to mention a cam that makes power up to 7400 may actually peak at 6500 once in the engine, depending on heads and intake. and again, some people cant tell this and continue wringing it out to 7400 while they tune it at the track.

IHI

iTrader: (1)

There's a ton of guys beating the snot out of their equipment for reasons like you just mentioned, they throw parts at an engine and use "advertised windows" of where things "should" be making power...when the reality of the situation they're usually losing performance. the cam i have/had in my junk was advertised upto 6800rpm...it peaked hp @ 6300 and then fell off from that point on. But with the engine dyno it allows you ALSO to spec out the 3rd most imporatnt piece of the puzzle...the convertor, IMO it falls a close 3rd to the heads and cam in overall performance, hence why they're so expensive for GOOD convertor and not the junk being bought for $2-300 (they work/get a person down the track but it's like buying a set of lets say, refurbished vortec heads compaired to AFR's or the like.) They work, but your leaving performance on the table...engine dynoing allows you to spec EXACTLY the flash rpm needed and the convertor company i use has hit the mark exact everytime we give them dyno info along with car info, they flash exactly where they should be....vs freinds of mine that throw stuff together, call a convertor company and try to use math/guesstimates to pick a flash point since they did'nt dyno to find out the REAL peak tq rpm.

For years i thought it was a waste of time/money, but after we did our first engine i wanted to beat my head on a wall for being so stupid and not doing this years prior...would've saved soo much time, soo much money, soo much equipment wear and tear. And for the record your not going to find "a considerable amount more hp" tuning at the track unless the dyno operator and dyno you used was a POS. The engine itself is what it is, it's not going to stop making peak hp @ 6500rpm per say just because you put a power glide behind it vs a TH350 or TH400....the engine is it's own component, all self contained, it's going to put out what it puts out at every increment regardless of your drivetrain, how is changing from a 28" tire to a 30" tire going to change rpm band, peak hp/tq of the engine???? It will change the way the convertor puts the power down, but not what the engine is putting out. So that's all i'm trying to convey to the arguement of being able to find more power on the track....the only variable at the track that will affect the engine ONLY will be the air for better/worse...and the only guys i see tuning their junk each race in brackets are the fools that load up 1st/2nd round and heading home....there's just not going to be a considerable gain to warrant messing with anything unless there's a HUGE change in the air...i run my stuff scarey lean, i'm usually .3-.4 slower tuned for racing than i am on kill trying for a time slip...so when the fall gets here i have no choice but to jet up a bit so i dont blow stuff up.

skinny z

The comments regarding the convertor I find very interesting because for the first time, I could see where the convertor flashed to when the throttle was mashed.( I even have the event recorded on video and can see the rpm jump and then start to pull.) Something that's difficult to do when at the track and concentrating on cutting a good light and nailing the first shift.

IHI

iTrader: (1)

Exactly, that's why anybody trying to argue that dynoing is a waste of time, effort, and money obviously has'nt been on one, too much good information to be gained to make the car perform the way it should...there is alot of power left on the table with many combinations that guys just throw to gether old school and drop in a car...but like i said, until you've done it and tuned with one, ya dont know what your missing.

JesasaurusRex

iTrader: (3)

First and foremost my friend, i was a we bit buzzed last evening
That being said yes you can ball park a motor very quickly and conveniently on a dyno. What i'm trying to get at is a motor and or a chassis reacts differently when in real use. Nothing more nothing less.

IHI

iTrader: (1)

I'd be lieing if i said i never responded to a post half crocked but the fact of the matter is, like it or not, a dyno is some of the best money ever spent. You will find optimum a heck of alot faster and a heck of aslot cheaper than just building a grinder and throwing it between the fenders...BUT trying to use the numbers your given to brag with is hog wash..post the time slip and then we'll talk

skinny z

All said and done, as an enthusiast, I think you owe it to yourself to try a dyno.
There is info to be had, even if it's only a confirmation of what you may already know.
As far as bragging goes, I may bring up the numbers if they were a little more impressive AND had the time slips to prove it.
Incidentally, they DO race dynos and offer cash prizes. At least for the biggest numbers.