Who's dynoed their 07 Tahoe ?
- Thread starter VF1000R
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Here is a post that I wrote a while back - this should give you an idea of what to expect (keep in mind the HP loss through the drive train - the posted 320HP from the factory is at the crank shaft... not rear-wheel...
Previous post -
I have a 2007 Z71 - with K&N Cold Air Kit and Flowmaster Catback - I decided to go with a custom tune versus mailorder or chip - mainly due to the fact that there is a shop local to me (Durham, NC) - that owns a dyno and specializes in GM Tuning - Carolina Automasters (www.carolinaautomasters.com); I would gladly attach the dyno sheet - but I'm having technical difficulties attaching it (something about the size not matching up). I would be more than happy to email it to anyone interested.
The numbers are:
My initial run - 264 HP @ 5500 rpm (basically redline); 279 ft-lbs torque @ 4500 rpm
After a few runs/tunes - 262 HP @ 4800 rpm; 298 ft-lbs torque @ 3900 rpm
Key points - I picked up 25 ft-lbs of torque at the real-wheel the entire duration from 2500 to 4500 rpm; I also picked up about 20 hp the entire duration from 2500 to 4200 rpm; You really have to see the sheet to appreciate the difference - it is slightly misleading that I lost 2 HP overall - because that was at redline versus what I gained in all the "driveable" rpm range.
Huge difference in driving the car - the transmission shifts are alot crisper, the throttle response is 100% better - I definitely would recommend this shop to anyone. I can't speak for the gas mpg - I haven't been able to keep my foot out of the gas yet.
73shark
Full Access Member
Did your tuner take out any of the torque mgmt?
Yes - he got rid of that
You're telling me that there appears to be about a 17% loss due to drive train ? U 2WD or 4 WD ? And this was after you already had the CA and Flowmaster installed ?
73shark
Full Access Member
A drop of 16%-20% is considered about normal.
It seems like there is more left on the table for you there. Under no circumstances should you lose HP. At the very least, you should maintain the stock HP up top. Just because you gained torque down low, doesn't mean you cant gain torque up top as well. (HP= (torque X RPM)/ 5252)
There is no reason for you to have lost torque at 4800 RPM and above. Something is not right.
One clarification point - the KandN Cold Air Kit and Flowmaster Catback were on my Tahoe before I had it Dyno'ed.
Also - I did not lose torque at 4800 RPM - my Torque and HP numbers are significantly above (the first run - not stock b/c I had the cold air and catback on) from 2200 - 5000 RPM; however - they seem to drop off after 5200. I was concerned about that at first; however - the Tahoe Redlines at 6000 - (and I need to go take mine out for another spin to confirm the accuracy of this comment - but I think that most transmission shifts ((from drive - with pedal to the floor)) are around 5000 rpm - unless its in 4th gear over 120 mph - when it starts to creep up to 6. So - I hear you on the "it shouldn't go down at the top end" - but i'm wondering if I would even notice any gains over 5200 RPM. The other reason I didn't press hard on this while I was getting mine tuned is - that it is a little un-nerving to hear your 45K dollar vehicle with less than 5K miles on it hit 6000 rpm (from 3 feet away)- so I was not wanting to hear the shop wind it up that high again, and again, and again... The only other thing that might be worth mentioning from my dyno sheet is that the air/fuel ratio (from the first to the last run) appears to come together (meaning - being the exact same) at 5300 RPM - whereas - up until then it is significantly different.
Please let me know your feedback... I had reached out to Justin before I had this shop do my tune and he had heard of the guy before. The only reason - I didn't go with another option is that I wanted it tuned at a Dyno shop - just to see the numbers. The website of the place - is carolinaautomasters.com - and the main guy there has tuned over 1200 vehicles out of the shop -as well as- has good feedback around town.
Again - please let me know your thoughts...
Ah yes, I had a brain fart, I was comparing torque gains at 4800 to the stock output at 5500.
What was the tuned HP at 5500? For best acceleration at full throttle, you should shift after peak HP which should be around 5700.
What was the tuned HP at 5500? For best acceleration at full throttle, you should shift after peak HP which should be around 5700.
You will be correct - (as I mentioned earlier) my HP and TQ - seem to fall below the initial run numbers at 5200 RPM to Redline 6000; So - to answer your question the HP at 5500 RPM after the tune is 240 HP.
I'd be happy to email u the actual dyno sheet for you to review. Also - do you or Justin have a dyno sheet from a 2007 Tahoe that he has tuned? I'd like to compare them...
If the tune was still stock above 5200, then there would be more power on the table. You should never see anything fall below the stock tune numbers. My guess is that if power is less then it detonated. This biggest issue I see is while you gained hp at 4800rpm you lost 24hp at 5500rpm. Seems like whatever changes were made they were worse than stock above 5200.
Unfortuneatly we don't have any 07 Tahoe dyno sheets as only a few sheets are actually kept. All of our data is kept in log files.
Unfortuneatly we don't have any 07 Tahoe dyno sheets as only a few sheets are actually kept. All of our data is kept in log files.
Keep me posted - if you come across any dyno sheets. I agree - I was concerned about the drop off above 5200 RPM. Here is the positive... I did run mine against a buddy of mine's 2007 Silverado - a few times - low end and top end - and it wasn't even close!!!
Can both of you post your dyno sheets (baseline and after mods) and also do you know what gear was used? I am curious what the area under the curve and the air/fuel ratio looks like.
Yeah, you should not lose 20 hp up top. From your description, it seems like power was shifted to the lower rpms (more daily usability) versus up top. As long as the A/F ratios are inline and you are satisfied with the results (more mid-range power), the tune should be ok. If you don't mind, how much was the dyno tune and is there a way to switch back to factory settings during dealership visits?
Yeah, you should not lose 20 hp up top. From your description, it seems like power was shifted to the lower rpms (more daily usability) versus up top. As long as the A/F ratios are inline and you are satisfied with the results (more mid-range power), the tune should be ok. If you don't mind, how much was the dyno tune and is there a way to switch back to factory settings during dealership visits?
Zed 71 - good point... I did indicate to the guy doing the tune that I was most concerned about the increase in (daily usage and the drivable rpm range) - I might add some more tricks to mine soon - if so i'll get a follow up appointment at the dyno shop (and take more note of the top end - but i'm pleased with the way it runs)
I paid either 300 or 350 - and if I need to take mine into the dealer for work - i can bring it back to the dyno shop - to reset to factory or reset to the tune (for free).
I tried posting my sheet before - and I couldn't make it go through. I'd be more than happy to email it to you (just send me an email address)
Power shouldn't be shifted since it's not a mechanical change like a camshaft.
This is an efficiency improvement which can occur across the board. Do you have any pinging?
I will have to scan the dyno sheet to post it up. I will see what I can do.
This is an efficiency improvement which can occur across the board. Do you have any pinging?
I will have to scan the dyno sheet to post it up. I will see what I can do.
The power shifting comment was more of an observation based on the text description that was provided. Yes, typically a power shift is obtained through a change in camshaft (move the powerband to higher rpms assuming the internals can handle it).
Granted I am more familiar with tuning of Japanese engines, but we have seen a mid-range 20 hp increase in the area under the hp curve (w/ minor loss at peak ~4 hp - not a power shift) by addressing volumetric inefficiencies of the VQ series engines. Not saying this can be universally applied to other engines; the VQ had less air being recovered by the front two cylinders due to the front angle of the top plenum.
Granted I am more familiar with tuning of Japanese engines, but we have seen a mid-range 20 hp increase in the area under the hp curve (w/ minor loss at peak ~4 hp - not a power shift) by addressing volumetric inefficiencies of the VQ series engines. Not saying this can be universally applied to other engines; the VQ had less air being recovered by the front two cylinders due to the front angle of the top plenum.
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