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Thread: Went to the dyno today

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Posts: 1-10 of 58
2009-05-13 11:51:09
#1
Went to the dyno today
Finally went to get the VE motor tuned a bit today.

Overall I think I'm a little disapointed with the results, although the car feels pretty good on the road. We're at 1660ft above sea level, so there is aproximately a 16.6% loss in power for a NA car here.

The run was done at mid day so temperatures was very hot, and the motor was just finished tuned. The tuner spent about 30 mins in total between 5k rpm and redline. So I'm sure with some more finetuning the results could improve.

actual numbers 181whp and 191nm torque at 7500rpm. Converted to sea level that's about 181*1.166 = 211whp and 191*1.166/1.35582 = 164lb ft

Will only be able to scan and upload the dyno chart tomorrow when I'm back at work though.
2009-05-13 12:15:57
#2
Doctor G, I was taught that you lose 3% HP per every 1000 feet. That being said if you are at 1660 feet that would be arouns 5% total but lets round it out to 6%.

6% of 181 is about 10.5 HP loss. If we just rounded it out to 11 HP you would be up at about

181 + 11 = 192 WHP.

I am not saying my calculation is right I am only putting out what I heard. I am going to check into it some more.
2009-05-13 12:31:29
#3
Yep it seems that 2.5 to 3 % is the correct HP % loss for every 1000 feet. So you will be losing no more than 5% of your actual WHP at 1660 feet above see level.


So your total power figures are.

191 WHP and 148 Lb Ft of torque to the wheels.
2009-05-13 13:19:51
#4
i was gonna say,dissapointed with 211whp!!?
what are your mods?
2009-05-13 14:29:18
#5
Originally Posted by Andreas
Yep it seems that 2.5 to 3 % is the correct HP % loss for every 1000 feet. So you will be losing no more than 5% of your actual WHP at 1660 feet above see level.


So your total power figures are.

191 WHP and 148 Lb Ft of torque to the wheels.


Andreas where do you get those figures from about power loss at altitude? I've never read anywhere about it formally.

Reason I ask is because we have seen it countless times on the dyno and the average loss between say Cape Town (sea level) and Jo'burg (1660ft) has been consistantly around 16-17%.

Take a bone stock SR20 rated at 140hp (105kw) at the fly. These will dyno at 105whp (78wkw) all day long.

Same with the VE's. 187hp stock. Dynos at 140whp up here consistantly.

Apparently 16% loss for altitude, and we put the further 15% loss down to drivetrain losses.

i.e. 140hp/1.16/1.15 = 105whp up here.


Mods are sr16ve pistons, FS4 cams, itb's, 3" exhaust, custom 4-1 header (needs a redesign) and management.

The reason I'm disappointed is because a stock sub assembly VE with perhaps a shaved head and sr16ve cams made 173whp on that same dyno. For the mods I have I should be putting down more. Either that or the FS4 cams really do not do these motors justice.

Now, I just went for a drive and when I got back I noticed the motor had popped one of the small welsh plugs out the side of the head (near the FR engine mounting). Oil everyewhere. WTF? I know the motor doesn't have any vacuum right now as there is no IM. Any ideas??
2009-05-13 15:05:50
#6
Google HP loss and altidtude and you will see, that 3% of HP is lost for every 1000 feet you go up from sea level
2009-05-13 15:08:39
#7
This has to do with the correction factor on the dyno .. .what type (of dyno) is?
thanks.
2009-05-13 15:09:10
#8
Here is your calculator

Wallace Racing - Braking HP Loss at Altitude Calculator

if you have 192 HP at sea level and you type in 1660 feet you will get 9.56 HP loss
2009-05-13 15:16:46
#9
Originally Posted by Andreas
Google HP loss and altidtude and you will see, that 3% of HP is lost for every 1000 feet you go up from sea level


Okay okay stop the bus. My bad. We are at 1740meters above sea level. Not feet.

Thus, 5707ft altitude. 3%*5707 / 1000 = 17% which explains everything.

So we can assume at altitude my power figure would be around the 210whp mark... give or take 2-3 hp.
2009-05-13 15:23:27
#10
If you say you make 181 WHP the dyno has already corrected the WHP figures and calculated in the drive train loss of your car.

Now if you said you car made 181 WHP then the car will make about 201 Crank HP

If you factor in a 3% loss from see level that would be 192 WHP or 213 Crank HP.

Every car will have a diffrent drive train loss so saying 15 % is not a general rule.

Generally a SR20DE making about 140 HP makes 123-126 WHP at sea level which equals a about 10-12 drive train loss.
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