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Considering whether to modify engine parts


Marios

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Let's hopefully dispell some myths

 

First, there are several bolt ons that will make power - it all depends on what specific items we're talking about, and what year the car is. Test pipes, high flow cats, spacers, many exhausts, all will net some decent gains on most cars. My own car went from a baseline of 225 whp to 257 ish without a tune, to 269 after a tune.

 

Doing a series of runs before hand, and a series of runs afterwards, logging things like TPS (throttle position), Injector Duty Cycle (IDC) and Timing, and using a wideband 02 sensor. With that data, you can then see exactly what the car is seeing, and see exactly how the ecu is reacting to the changes that have been made. Of course, every car is like a fingerprint, so it's not unusual for 2 cars to have different reactions to the same modifications..but they will generally fall into the same categories.

 

It's also important to either use the same dyno each time, or, to ask the dyno operator what cars similarly prepped put down. This will at least give you a general idea of where you fall relative to where it should be. Switching between dyno's can create annomolies that confuse things. For example, when I first built my engine back in 2007, I spent about 900 miles breaking it in per my engine builders suggestions. I then brought the car to my tuner, a friend of mine at a shop in Connecticut (as I don't own a dyno). After he mapped it (UTEC) we netted a final result of 302 whp. This was on a Dyno Dynamics. I then drove the car for over a year and a half, and over 10k miles. Last fall, I took a weekend trip down to Maryland to see a friend of mine, who happens to work at Turbo XS. We put the car on his dyno (Dynapack) and low and behold, it put down 303.9 whp. I had made zero changes to the hardware or software of my car from the original July 2007 tune till the one in Fall 2008. From there, we did some changes to the map, and found another 16.5 whp - culiminating in a final # of 320whp. Keep one thing in mind guys, the # is really quite arbitrary IMHO. The net change in not only the #'s, but the shape of the curve, is what you're interested in.

 

I am personally not a fan of the popcharger, but many use it because of it's low cost, and sound - nothing wrong with that at all. Just realize that you will likely net the same power figure with a stock airbox. This is especially true for 2006 cars which have a slightly revised airbox from the factory vs 2003-2005 models (the 2006 ones have a nice venturi built in).

 

Don't always rely on the "butt dyno" - sometimes we perceive gains where there are none, and vice versa.

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Thanks for the informative post Adam. I'm amazed that you only saw a 2BHP difference from one dyno to the other, I've seen more variation than that between 2 DynoDynamics dynos before.

 

My own car went from a baseline of 225 whp to 257 ish without a tune, to 269 after a tune.

What mods were used to achieve this? My car made 240WHP on a DynoDynamics, but I have a feeling that the popcharger negated any gains I got from my plenum spacer (intake temps were quite high, much higher than ambient). Also how did these mods effect the torque curve? I seem to remember that a member on here (maybe Ian) fitted decats (testpipes) and although it netted him some top end power, he lost quite a lot torque low down. I guess a remap might sort that bit out though.

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Thanks for the informative post Adam. I'm amazed that you only saw a 2BHP difference from one dyno to the other, I've seen more variation than that between 2 DynoDynamics dynos before.

 

My own car went from a baseline of 225 whp to 257 ish without a tune, to 269 after a tune.

What mods were used to achieve this? My car made 240WHP on a DynoDynamics, but I have a feeling that the popcharger negated any gains I got from my plenum spacer (intake temps were quite high, much higher than ambient). Also how did these mods effect the torque curve? I seem to remember that a member on here (maybe Ian) fitted decats (testpipes) and although it netted him some top end power, he lost quite a lot torque low down. I guess a remap might sort that bit out though.

 

My torque was down to 240 ft/lb with decats in & 242 ft/lb with sport cats. Steve also made similar torque figures with sport cats.

 

My exhaust setup is a bit strange though, I essentially still have decat pipes but they have been made into sport cats which is why I still get a lot of CELs.

 

The dyno operator said last week that the popcharger was not helping my figures :)

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Im still trying to get my head around how the plenum spacer would actually add bhp, my understanding is that it just holds the engine into place right?

 

 

it's the air flow chamber. air to the front two cylinders is improved with a plenum spacer which with the oem plenum is slighting lacking. So this improves the bhp slightly

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Im still trying to get my head around how the plenum spacer would actually add bhp, my understanding is that it just holds the engine into place right?

 

 

The plenum spacer (or aftermarket plenum) redistributes air across all six cylinders more evenly. It adds midrange so probably fattens out the curve a little.

 

I wouldn't have thought peak BHP would be affected much to be honest.

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Thanks for the informative post Adam. I'm amazed that you only saw a 2BHP difference from one dyno to the other, I've seen more variation than that between 2 DynoDynamics dynos before.

 

My own car went from a baseline of 225 whp to 257 ish without a tune, to 269 after a tune.

What mods were used to achieve this? My car made 240WHP on a DynoDynamics, but I have a feeling that the popcharger negated any gains I got from my plenum spacer (intake temps were quite high, much higher than ambient). Also how did these mods effect the torque curve? I seem to remember that a member on here (maybe Ian) fitted decats (testpipes) and although it netted him some top end power, he lost quite a lot torque low down. I guess a remap might sort that bit out though.

 

My mods at the time:

 

Gruppe-M intake

Unorthodox Racing crank pulley

Ultimate Racing ceramic high flow cats

Ultimate Racing Y pipe

Apexi World Sport 2 exhaust

 

I then had a reflash done to my ecu in fall 2003. Drove the car that way till Turbo XS got me a beta tester UTEC in December 2005. I'd have to try to find the dyno sheet from when I got the reflash done - the gains were noticeable though, about 8-10 whp and about the same in torque if I recall. The reflash was done on my car, not as a mailorder thing (I personally don't like those but that's just me)

 

By the time I was tuned on the UTEC, the only part I had changed was the exhaust, to a Fujitsubo Titanium - everything else remained the same.

 

this is my dyno sheet from my pre UTEC tune (running reflashed ecu) compared to post UTEC tune - the gains were noticeable, and substantial

 

http://www.z1auto.com/images/scan.pdf

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  • 2 weeks later...

All I know is that I have a pop charger, plenum spacer and Nismo exhaust and on the DynoDynamics dyno it made 2BHP over stock (so I call that stock!) so it obviously does dial out mods. Unless of course the popcharger lost me what the plenum spacer gained me. AFR was spot on too by what the chaps there were saying.

 

 

 

isn't the stock intake better than a pop charger in terms of air supply to the engine?

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