Got my 98 GS400 on the dyno
04-27-14, 08:25 AM
#1
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Got my 98 GS400 on the dyno
So yesterday (April 26th) I attended my friend's carmeet/dyno day event here in DFW. I was reluctant to do it, but thankfully the car came out fine. 
Car's mileage: 257,xxx miles
Mods: Rear muffler delete
Dyno: Mustang
Weather Corrected Results: Yes
My car got 3 pulls, the best of which had the following results, very consistent, if a little confusing perhaps:
239 hp
237 lb-ft of torque
Due to the automatic trans downshifting from 3rd into 2nd every time we went WOT, the lowest point we got the car to go WOT in 3rd was at over 4000 RPM, so the reading was probably missing some key (higher peak?) torque data.
Now here's the weird bit. ImportTuner magazine online has an article where in 2002 they dyno'd a stock '98 GS400 that put down 237 hp and 254 ft-lb torque ---- on a Dynojet! They mentioned the car was dyno'd from 3750 RPM due to the same auto downshifting issue, although mine took 4000 RPM to achieve the same.
I'm guessing the rear muffler delete may have attributed to the higher hp and lower tq numbers? Or perhaps starting at 4000-4200 RPM onward may have missed the peak torque range by a bit? I need to google the factory RPM range for peak torque to clear that up...
Anyway, was an interesting day! My brother's 99 Trans Am stock with a muffler and intake lid mods put down 293 hp / 310 tq! Not what we expected either, in a good way.
Car's mileage: 257,xxx miles
Mods: Rear muffler delete
Dyno: Mustang
Weather Corrected Results: Yes
My car got 3 pulls, the best of which had the following results, very consistent, if a little confusing perhaps:
239 hp
237 lb-ft of torque
Due to the automatic trans downshifting from 3rd into 2nd every time we went WOT, the lowest point we got the car to go WOT in 3rd was at over 4000 RPM, so the reading was probably missing some key (higher peak?) torque data.
Now here's the weird bit. ImportTuner magazine online has an article where in 2002 they dyno'd a stock '98 GS400 that put down 237 hp and 254 ft-lb torque ---- on a Dynojet! They mentioned the car was dyno'd from 3750 RPM due to the same auto downshifting issue, although mine took 4000 RPM to achieve the same.
I'm guessing the rear muffler delete may have attributed to the higher hp and lower tq numbers? Or perhaps starting at 4000-4200 RPM onward may have missed the peak torque range by a bit? I need to google the factory RPM range for peak torque to clear that up...
Anyway, was an interesting day! My brother's 99 Trans Am stock with a muffler and intake lid mods put down 293 hp / 310 tq! Not what we expected either, in a good way.
04-27-14, 12:04 PM
#2
Thanks for posting this. Very interesting info! I highly doubt a muffler delete would result in this kind of loss of TQ without showing a gain a bit higher up (peak HP/TQ). To me, the variability you mentioned in numbers posted elsewhere is related to the things you talked about (auto tranny related).
You sparked my curiousity so I searched for the Import Tuner article and found it if anyone is interested:
http://www.importtuner.com/powerpage...0_power_pages/
What's super cool I think is that you have 257K miles and are still putting down respectable numbers. These engines are awesome!
You sparked my curiousity so I searched for the Import Tuner article and found it if anyone is interested:
http://www.importtuner.com/powerpage...0_power_pages/
What's super cool I think is that you have 257K miles and are still putting down respectable numbers. These engines are awesome!
04-27-14, 12:11 PM
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Thanks for posting this. Very interesting info! I highly doubt a muffler delete would result in this kind of loss of TQ without showing a gain a bit higher up (peak HP/TQ). To me, the variability you mentioned in numbers posted elsewhere is related to the things you talked about (auto tranny related).
You sparked my curiousity so I searched for the Import Tuner article and found it if anyone is interested:
http://www.importtuner.com/powerpage...0_power_pages/
What's super cool I think is that you have 257K miles and are still putting down respectable numbers. These engines are awesome!
You sparked my curiousity so I searched for the Import Tuner article and found it if anyone is interested:
http://www.importtuner.com/powerpage...0_power_pages/
What's super cool I think is that you have 257K miles and are still putting down respectable numbers. These engines are awesome!
5.8 seconds on the friggin' dot!
And no, I kept the PWR mode off.
04-28-14, 03:46 PM
#5
Actually 235 - 245whp is the norm for a rather stock 2GS. IIRC my car did 244whp a while ago with just an intake and rear section exhaust. Then it did 264whp when I added the Apexi Neo and finally 282whp with the addition of 3rd batch S&S headers.
Good run though!!! Keep the mods coming!
Good run though!!! Keep the mods coming!
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04-29-14, 04:09 PM
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M mode is more of a "don't shift higher than X gear" than "only stay in gear X." That is why, when you shift up from 2->3 too early, but are pressing all the way down on the gas pedal, the car won't immediately shift into 3rd, it may continue to peak out a bit more RPM before going into 3rd. For that matter, you can come to a full stop, and keep the gear # 4, for example, and take off again. The car will go from 1.
I've read 21%
But yes, take 300hp and times it by .80 (which would be 100% - 20%) and you get 240, but most cars I've seen or read fall just a tad below given their age and maintenance, so IF the 20% figure is accurate, my car is running exceptionally well in terms of horsepower. Unfortunately, it would seem the dyno read the torque much lower than I would think, given the factory AT THE CRANK specs are 300 hp and 310tq (or so).In 2005 (or '06) the SAE got together and changed how horsepower is noted or given for an engine, to make it more 'accurate'. So, many car models starting in the next model year (06 or 07) displayed lower HP ratings even though they were otherwise the same car/engine. For example, some manufacturers gave specs using premium gas and others didn't. Toyota and Lexus had to change the figures for a few models (the Camry comes to mind, it went from 200 to 190 something hp). The rating is also affected by what accessories are attached (or not, such as power steering, etc.) for the engine dyno tests that manufacturers use to rate their engines.
As such, our 20-21% drive train loss is actually pretty terrible, but considering most manual FWD still lose about 10-12%, and auto FWD lose 15%, RWD AND AUTO at 20% isn't all that bad. And if you think that sucks, my '91 Land Cruiser AWD had something around 30% drive train loss with all those axles, wheels and gears, transfer case (they were rated at 155 hp but put down 89-90 awhp!)
Last edited by Sampak; 04-29-14 at 04:30 PM.
04-30-14, 01:37 PM
#13
I have driven my GS400 in M mode alot, and believe it or not, it will downshift regardless of which gear number shows up on the dash.
M mode is more of a "don't shift higher than X gear" than "only stay in gear X." That is why, when you shift up from 2->3 too early, but are pressing all the way down on the gas pedal, the car won't immediately shift into 3rd, it may continue to peak out a bit more RPM before going into 3rd. For that matter, you can come to a full stop, and keep the gear # 4, for example, and take off again. The car will go from 1.
I've read 21% But yes, take 300hp and times it by .80 (which would be 100% - 20%) and you get 240, but most cars I've seen or read fall just a tad below given their age and maintenance, so IF the 20% figure is accurate, my car is running exceptionally well in terms of horsepower. Unfortunately, it would seem the dyno read the torque much lower than I would think, given the factory AT THE CRANK specs are 300 hp and 310tq (or so).
I'm not sure why this is a surprise to you, but I'm assuming you've never seen another car dyno sheet before (?) (I was surprised when I first found out how it works!). Every major car maker in the world will typically give you the engine horsepower/torque at the CRANK, and even then there are many, many different things that can affect what the "true" power rating can be.
In 2005 (or '06) the SAE got together and changed how horsepower is noted or given for an engine, to make it more 'accurate'. So, many car models starting in the next model year (06 or 07) displayed lower HP ratings even though they were otherwise the same car/engine. For example, some manufacturers gave specs using premium gas and others didn't. Toyota and Lexus had to change the figures for a few models (the Camry comes to mind, it went from 200 to 190 something hp). The rating is also affected by what accessories are attached (or not, such as power steering, etc.) for the engine dyno tests that manufacturers use to rate their engines.
As such, our 20-21% drive train loss is actually pretty terrible, but considering most manual FWD still lose about 10-12%, and auto FWD lose 15%, RWD AND AUTO at 20% isn't all that bad. And if you think that sucks, my '91 Land Cruiser AWD had something around 30% drive train loss with all those axles, wheels and gears, transfer case (they were rated at 155 hp but put down 89-90 awhp!)
M mode is more of a "don't shift higher than X gear" than "only stay in gear X." That is why, when you shift up from 2->3 too early, but are pressing all the way down on the gas pedal, the car won't immediately shift into 3rd, it may continue to peak out a bit more RPM before going into 3rd. For that matter, you can come to a full stop, and keep the gear # 4, for example, and take off again. The car will go from 1.
I've read 21%
But yes, take 300hp and times it by .80 (which would be 100% - 20%) and you get 240, but most cars I've seen or read fall just a tad below given their age and maintenance, so IF the 20% figure is accurate, my car is running exceptionally well in terms of horsepower. Unfortunately, it would seem the dyno read the torque much lower than I would think, given the factory AT THE CRANK specs are 300 hp and 310tq (or so).I'm not sure why this is a surprise to you, but I'm assuming you've never seen another car dyno sheet before (?) (I was surprised when I first found out how it works!). Every major car maker in the world will typically give you the engine horsepower/torque at the CRANK, and even then there are many, many different things that can affect what the "true" power rating can be.
In 2005 (or '06) the SAE got together and changed how horsepower is noted or given for an engine, to make it more 'accurate'. So, many car models starting in the next model year (06 or 07) displayed lower HP ratings even though they were otherwise the same car/engine. For example, some manufacturers gave specs using premium gas and others didn't. Toyota and Lexus had to change the figures for a few models (the Camry comes to mind, it went from 200 to 190 something hp). The rating is also affected by what accessories are attached (or not, such as power steering, etc.) for the engine dyno tests that manufacturers use to rate their engines.
As such, our 20-21% drive train loss is actually pretty terrible, but considering most manual FWD still lose about 10-12%, and auto FWD lose 15%, RWD AND AUTO at 20% isn't all that bad. And if you think that sucks, my '91 Land Cruiser AWD had something around 30% drive train loss with all those axles, wheels and gears, transfer case (they were rated at 155 hp but put down 89-90 awhp!)
05-01-14, 08:22 AM
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Actually 235 - 245whp is the norm for a rather stock 2GS. IIRC my car did 244whp a while ago with just an intake and rear section exhaust. Then it did 264whp when I added the Apexi Neo and finally 282whp with the addition of 3rd batch S&S headers.
Good run though!!! Keep the mods coming!
Good run though!!! Keep the mods coming!
How 'difficult' is it vs. cost benefit for example if I were to use it on my car as it sits (Muffler delete). Or is intake at least recommended to get anything out of it? Can it be used to 'fine tune' a stock-ish car? Any dangers (other than screwing up far too lean of course). I've seen folks get decent 5-10% increase in WHP so I'm just curious what I can do without blowing up the engine.
I'm thinking of actually getting a custom mandrel bent 2.5" exhaust or at least some similarly effective cheap aftermarket bits (y-pipe, axlebacks) and get rid of the old triple resonators and 'custom' muffler delete hodge podge my car currently came with, in the future.Also, headers -- seems like a good bit of $$$$ but I take it it's got the biggest kick in the can if that is all I did? Any emission issues?
Last edited by Sampak; 05-01-14 at 08:26 AM.