In a couple weeks I am going to a friend's shop in Nashville who owns a chassis dyno, I was wondering what the guess's would be to how much hp an 03' STR will actually put to the wheel and if you guys have any ideas on things to try to get more hp out of the car without a major overhaul. I will have full access to as many pulls on the dyno as necessary. My car is fairly straightfwd, has a modified intake similar to many that I have seen on posts here and I also have custom exhaust, only from the h-pipe back new mufflers, so maybe a few hp gain from stock but nothing major. I may put on an aftermarket pulley when I am down there and see what I get out of that but I just replaced the stock one and belt so I may hold off to get some of my money's worth.

If any of you have some feasible ideas, please post, and I will try to incoporate and post some results, I expect to be down there May 7-9, so dont expect anything until then.

 

From what I know, a stock S-Type R, XKR, or XJR should put out right around 315rwhp. With your revised intake and exhaust...I would put it around maybe 325 or 330rwhp? There are a lot of different things to take into account though...temperature, mileage, condition of the motor etc.

I look forward to hearing your results. Take a video!

 

I will be sure to take a video and thanks for the reply on the pulley post as well, I most likely will end up getting it, hopefully between the pulley, trying different options with the intake, and maybe an exhaust modification (opting for a x-pipe replacement as well) I may be able to get a good combo and post.

 

Glad to help.

One question though...how loud is that H-pipe configuration that you have now?

 

I guess I say h-pipe but I am just referring to the stock exhaust pipes where they join and seperate prior to going to the mufflers and that may not be the most accurate description. Honestly sound was my biggest worry, I wanted some but not a ton, and with the new mufflers its not that bad which is why I may go one step further and put in an x-pipe (which is actually suppossed to lower the decible output and clean the sound up more). Right now at idle its very low deeper sound, noticable when standing behind the car, and it produces a clean note through harder acceleration that is noticable inside and outside of the car, normal driving doesnt produce this. I went with magnaflow mufflers (center to offset) and welded them on with new tips etc, kept the original piping had to modify the hangers just a little. It was a good start and we will see what we can do this time.

 

From what I can remember a good run on a dynojet type (so 1 big drum per wheel instead of 2 small drums per wheel), no heat soaked engine, tires inflated right (I always use 2.5 bar, to keep dynos comparable) etc, you should be able to pull 330-340 rwhp on a 4.2 supercharged car if they are in good shape. The 4.0 cars seem to be around 310 rwhp mark.

Andre.

 

What numbers did you get?

 

This wont be a dynojet but the two small drums, which are supposed to be more accurate, there is a lot of science to this that was explained that I cant recall.

 

Only a single drum dyno is able to come close to true rwhp, there is no doubt there. Best are also those that are able to provide resistance via a eddy current system, as load will generate a more realistic figure. A dual drum is used to calculate engine bhp, as on these systems you would do a rollout and measure the resistance in hp there to come to an estimated bhp. For the latter it becomes an estimate, as in a rollout no load losses are incorporated and also no torque converter slip for instance. So for anyone providing dyno numbers,At least mention on what system the rwhp has been measured.

Andre

 

Avos does have a point. A dynojet vs. a dyno with the two drums do read different. As he stated above, a dynojet measure true rwhp while the dual-drum dyno more or less estimates/measures power at the engine.

Either way, since you will be doing before and after runs with the pulley, it will be cool to see the gains regardless of what dyno is being used.

 

Its a two roller system with an Eddy current resistance system (a brake essentially on the front roller to provide the load) from Dyno Dynamics that measures the force that the wheels are exerting, these are suppossed to be more accurate than the standard dynojet that meausres the inertia force of the car pushing the one large roller. Many times this can result in a lower rwhp under the Eddy system. I realize enthusiasts can argue this point all day long (however if you do the research it would seem to point to Eddy systems over inertia systems the majority of the time)......if you want I can get the science guy explanation for it, the shop I go to has owned both and they put their money in their current system for more accurate numbers and tuning abilities.

 

Hahaha yes, lets not get into any flame battles on which form of measurement is better/more accurate. Either way, since I assume you will be going to this dyno to run your baseline and then with your supercharger pulley, we will be able to see the amount of power gained.

This number should be the same regardless of which dyno is used. If your dyno says you gained 15rwhp, a dynojet should reflect the same gain. That's all I really care about.

 

Hah, I agree but lets fuel the fire just a little bit, from a recent article:

Why is a loading dyno (Dyno Dynamics) better than an inertia dyno (dynojet)? - Loading dynos are better than inertia dynos for a number of reasons.

A) Steady State Tuning - Steady state tuning is the highlight of the loading dyno. Because the loading dyno uses an electric brake to keep the rollers from accelerating it is able to precisely vary how much load is placed on the cars engine. When the dyno exerts as much load on the engine as the engine is putting out, the rollers will stop accelerating and hold a constant speed. Because the engine is not accelerating we call this a steady state. During this time the dyno is measuring the load between the brake and the car and outputs a live power number. This is very useful for tuners because it allows them to make changes to each part of the ignition/fuel map and monitor the power gains or losses in real time. With an inertia dyno there is no way to keep the rollers from accelerating and therefore no way to hold a steady state. The engine simply accelerates through the ignition/fuel maps too quickly.

B) More precise measurement - Because inertia dynos use a heavy mass to simulate the inertia of the car being tested it is hard to monitor minor changes in power. The large mass of the rollers results in very minor changes in roller speed that inertia dyno sensors have a hard time picking up. If the sensor and computer don't see the change in roller speed the the dyno graph will not show a dip in power. However, a loading dyno uses rollers with very little mass and directly measures power rather than calculating it. Quick drops in power will be picked up by the load sensor and will show on the dyno graph. This is very useful for finding problems and ensuring that your engine is running correctly.

C) Load can be controlled - With an inertia dyno the load exerted on the engine as it accelerates is based on the inertia of the dyno rollers. This inertia is set by the mass of the rollers and is not able to be changed. The inertia of the dyno rollers directly determines how fast the cars engine will accelerate through each gear. Ideally this inertia would be equal to the inertia of the car being tested but this is rarely the case. The inertia is almost always going to be higher or lower than the inertia of the car and as a result the engine accelerates faster or slower than it would on the street. This can have a bearing on how the engine is tuned and how accurate the dyno replicates real life conditions. Because a loading dyno is able to actively alter the load on the rollers it is able to change the rate of acceleration as the operator pleases. Realistic loads for the particular vehicle can be used or loads simulating driving up a hill can be used. This is easily controlled by the dyno operator.

D) Problem Diagnosis - This feature goes back to the ability to control load and do steady state tuning. A loading dyno is able to simulate road conditions in a safe environment while allowing the technician to monitor the car and it's engine. An inertia dyno is unable to accurately simulate all but a few road conditions making it much more difficult to diagnose problems

 

Hmm...I need to try out this dyno to see how the numbers differ...

Interesting stuff. Good read.

 

I use a 1 drum dyno with the eddy current, so all sales points you mention apply ;-).

The Dual roll systems cause more resistance on the tire, just think about it, 2 small drums pushing the tire, or one large drum...

There are some tuners that swear by the twin roll systems (not the cheaper Dyno Dynamics, but the better Maha systems), and admit that these are not to be used to measure rwhp. They believe however that the calculated engine HP is very close.

Nevertheless, indeed the dual roll will give a lower rwhp (like mentioned above), so if you dyno, just mention on which dyno, then we can interpret it our own way.

Andre.

 

as I said before the debate is endless. FYI the car mostly doesnt even contact the second roller during a run, sometimes not at all, it rolls up firmly against the front one with the Eddy break, where the push/resistance is applied (no break or 'push' from the second roller, its not hooked to anything to provide resistance), oh well enough said about that.

But of course I will spell it all out as well as possible and to Patrick's point we will see what the change is from the updates. In the end, still no ideas of how to get any more hp gains? The 3lb. pulley will go on, exhaust will be modified (again), and the intake modified (again), hopefully will manage to get something decent to share with the group.

 

I dyno-ed my v6 s-type this Saturday, what a disappointment, the max hp was 183, this was a sad day for me. I plan on seeling the S-type now and maybe purchasing a S-Type R. We will see when I come back from vacation.

 

now would be the time super_jag, I couldnt believe how low the price has gotten on the R's (even the low mileage newer ones), the XF release really drove the price down...or you could hold out for the 2010 XFR...

 

I ask again. Did you get numbers yet?

 

Haha idk thats a hard choice Evan.. an S-Type R for under $15k or a XFR for $80k+.... What do you think super_jag?