UPSET w/ DYNO [Archive] - Cherokee SRT8 Forum

: UPSET w/ DYNO


FastSRT8GC
04-02-2007, 08:45 PM
Here is my dyno run pre Heads/Cam/Headers/B&G.

I have a volant CAI and B&B

http://www.cherokeesrt8.com/gallery/watermark.php?file=284&size=1

live4skins
04-02-2007, 09:13 PM
Arghhhh! What the heck is up with those numbers? Uh thats lower than stock numbers. Are your PP heads on? That just doesnt make sense....

FastSRT8GC
04-02-2007, 09:16 PM
Arghhhh! What the heck is up with those numbers? Uh thats lower than stock numbers. Are your PP heads on? That just doesnt make sense....


NOTHING just B&B with the volant.... the kicker is I ran a 13.1 @ 104

It was hot here today(upper80's) but how much does that affect things??

OH this was on a DYNOJET 2000 2wd Dyno

Cdog
04-02-2007, 09:27 PM
A lot of dynos are calibrated differently or incorrectly. The key is that you'll be able to see increases from changes.

FastSRT8GC
04-02-2007, 09:32 PM
that is what i am thinking. Because I pulled on a friends stock jeep when I ran the 13.1 and he ran 13.4/5 so its is faster.

This dyno would put his in the low 320's

GotStroke?
04-02-2007, 09:37 PM
Chris,
Your fourth gear dynos are going to read lower than others since most seem to use third gear. Also STD (SAE as well) correction accounts for weather related variables. Are you sure those aren't actual numbers?

FastSRT8GC
04-02-2007, 10:24 PM
Chris,
Your fourth gear dynos are going to read lower than others since most seem to use third gear. Also STD (SAE as well) correction accounts for weather related variables. Are you sure those aren't actual numbers?

These are the STD # the SAE were even lower!!

StageFright
04-02-2007, 10:31 PM
Dynojets give higher numbers than a Mustang dyno.

GotStroke?
04-02-2007, 11:42 PM
Dynojets give higher numbers than a Mustang dyno.

This used to be the case, but now it really varies by dyno; some MDs read like DJs, others do not. DJs were getting more business because they typically kicked out 7-10% higher numbers (some people claim 15% or more) which fed owner egos, even though MDs are clearly superior when it comes to actual tuning.
My Jeep was dynoed pre full exhaust (Dub, 176* T-stat) and put down 36Xrwhp and tq on a Mustang Dyno that reads like a DJ.

GotStroke?
04-02-2007, 11:47 PM
These are the STD # the SAE were even lower!!

Yeah 2-4% lower. I didn't see a correction factor on the graphs so I thought I'd ask.

Honestly your numbers aren't that bad IMO as I believe I've seen a 317rwhp dyno in fourth gear with a stock Jeep SRT8.

GRNENVY
04-03-2007, 03:03 AM
Dude dyno numbers don't mean ****. Dynos are for testing and comparing parts. It's a great tool to have but don't get stuck on them. Theres not two dynos on the planet that will read the same. **** most of the times you can't even compare hp/tq reading a couple hours apart . When I lived up north I had a good friend Joe at JD's with one dyno and Jim at JDM with another and they both read diff like 10-20hp. Your truck runs good and when we went to Bradenton it proved it. You ran a 13.10 in not the best condtions if this truck was up north like at atco you would have ran in the 12s. Also looking at the 60ft times 1.84s I think we were both spinning more then we thought. 1.75 short times would have been 12s all day in not the best conditions.

FastSRT8GC
04-03-2007, 05:15 AM
Dude dyno numbers don't mean ****. Dynos are for testing and comparing parts. It's a great tool to have but don't get stuck on them. Theres not two dynos on the planet that will read the same. **** most of the times you can't even compare hp/tq reading a couple hours apart . When I lived up north I had a good friend Joe at JD's with one dyno and Jim at JDM with another and they both read diff like 10-20hp. Your truck runs good and when we went to Bradenton it proved it. You ran a 13.10 in not the best condtions if this truck was up north like at atco you would have ran in the 12s. Also looking at the 60ft times 1.84s I think we were both spinning more then we thought. 1.75 short times would have been 12s all day in not the best conditions.

OK NICK, I will trust you. Since you are correct i does run out good. Just upset with all these 350's 360's on stockers. Oh well like you said those #'s dont mean jack at the track.

BuilderBill
04-03-2007, 05:22 AM
OK NICK, I will trust you. Since you are correct i does run out good. Just upset with all these 350's 360's on stockers. Oh well like you said those #'s dont mean jack at the track.
Fast,
I would have expected our numbers to be more similar, same Volant, both catbacks, no real other mods. Was the Hemi hot? Our A/F ratios are not similar either. WTH?

BDNJ
04-03-2007, 07:19 AM
Yeah 2-4% lower. I didn't see a correction factor on the graphs so I thought I'd ask.

Honestly your numbers aren't that bad IMO as I believe I've seen a 317rwhp dyno in fourth gear with a stock Jeep SRT8.


That stock 317hp 4th gear pull was mine. It was recorded on a Mustang awd dyno with a weight of 5050 (4850 truck +200 driver). Temps 77f, and 29.9 baro. I ran with hood closed, fan mod (on) and one addt'l cooling fan. I never ran it corrected to DJ #'s, but I have since I did added the mods below.

Mustang 359hp*/356tq*
Dyno 409hp*/408tq*

*This is with the stall converter drawing about a 10-20hp loss.

I have seen as much as a 10 hp - 15 hp loss on hot days - again on the dyno. The truck has made a least 15 trips to the dyno.:eek: Hoping to hit the track this friday.


Brendan

FastSRT8GC
04-03-2007, 08:20 AM
That stock 317hp 4th gear pull was mine. It was recorded on a Mustang awd dyno with a weight of 5050 (4850 truck +200 driver). Temps 77f, and 29.9 baro. I ran with hood closed, fan mod (on) and one addt'l cooling fan. I never ran it corrected to DJ #'s, but I have since I did added the mods below.


Brendan


Brendan, you mentioned the weight, i am not sure what they entered in for weight. maybe this is the problem. I dont know how all the info is sorted on these dynos. BUt with my times and mods these #'s dont seem correct.

we will try again with the b&G then again with the head and cam and kooks
:mad: :mad: :mad:

Blown-WK
04-03-2007, 08:37 AM
Dont be discouraged. My buddies SRT8 (exhaust, cai) was acting up on the dyno as well. The computer was acting a little goofy after the fuses were pulled out and I believe the Jeep needed a few runs to relearn the change. The first run was 308/312........second run 313/315........then the third run after 15 minute cooldown was 363/367. This was a brand new 2wd Dynojet 224xLC.

GRNENVY
04-03-2007, 09:16 AM
Mustang dyno uses diff load tables
Dyno jet doesn't work that way.



Brendan, you mentioned the weight, i am not sure what they entered in for weight. maybe this is the problem. I dont know how all the info is sorted on these dynos. BUt with my times and mods these #'s dont seem correct.

we will try again with the b&G then again with the head and cam and kooks
:mad: :mad: :mad:

StageFright
04-03-2007, 09:24 AM
dyno numbers don't mean ****.

A Dyno is a great tuning tool.
There are always going to be varibles between two different dynos, try to stick with the same one and watch weather conditions.

BDNJ
04-03-2007, 09:24 AM
Mustang dyno uses diff load tables
Dyno jet doesn't work that way.


I only know that there is an adjustment on the Mustang dyno to replicate DJ #'s. I have never been on a dyno jet.

GotStroke?
04-03-2007, 10:42 AM
Mustang dyno uses diff load tables
Dyno jet doesn't work that way.

+1. You don't need vehicle weight for DJs. DJs calculate TQ (then HP from TQ) based on how long it takes your car/truck to spin a known mass (the drums). MDs/Superflows use an eddy current brake to provide resistance and can therefore compensate for "load" which makes them a better tuning tool.