The planned program of bolt-on mods for my car has been completed. They pretty much cover the gamut of intake and exhaust with the exception of high flow cats and cams. Details of my mods and a copy of the dyno results can be seen at My Ride. In addition to the mods, I have had my ECU custom re-flashed by Technosquare to exactly match these mods.

No pulleys were changed out because my inquiries with several people who are technically familiar with the VQ35 consistently indicated that the OEM pulley employs essential dampening to protect the engine from belt harmonics which is not present in aftermarket pulleys. The consensus was that these belt harmonics are likely to result in engine damage over time.

High flow cats were ruled out because of noise. I installed the Borla TD exhaust in part because a number of posts suggested that it sounded essentially like stock. Obviously, the ones who made those posts had never heard one. My exhaust is two or three times as loud as stock and almost everyone who has ridden in the car in the last couple months has complained about the noise. And it has become noticably louder since the install. At this point, I’m giving serious consideration to reinstalling the OEM exhaust.

Every attempt has been made to obtain accurate dynamometer results. Pulls were made in fourth gear per my understanding that this represents a 1:1 drive ratio. The engine was cooled by fans and some water mist prior to test. Tests were conducted on a Dynojet dynamometer that is less than a year old by the racing shop owner who builds engines and does testing for the owner of Rock Falls Raceway, a local drag strip.

http://www.hitechmotorsport.com/

http://www.rockfallsraceway.com/

I have been given varying estimates of drive train loss percentages that range from 17% (on these forums) to 20% (Crawford Performance) to 25% (by AEBS, which considered that an AT loses 5% more than a MT). Thus, using the loss percentage MOST FAVORABLE to the car, the engine peaks at 290 HP at the crank. In other words, the output is roughly the same as a stock 350Z and my total gains for all mods MIGHT be 20 HP.

Here are my observations and conclusions. Your mileage may, and probably will, vary.

1. First, stopping just short of saying they are a waste of money, I will say that bolt on mods are a VERY expensive way to attempt to increase engine power and in the end, produce only a modest benefit at best.

2. The extra 500 or so rpm’s provided by the ECU re-flash are essentially worthless in my application. Power falls off so rapidly above 6500 rpm that it is senseless to wind the engine above this level, especially considering the increasing stress level experienced by the engine.

3. My earlier impressions that the mods made the car noticeably faster were apparently an illusion created by the louder exhaust in combination with that innate desire to want to believe that we got something for our money.

4. Unless I happened to pick the poorest performers out there, performance differences between different brands of products are basically hogwash. At this point, anyone would be hard pressed to convince me that any real world differences would be experienced between different brands of exhaust or intake components for example. Nevertheless, I seriously doubt that the spirited debates over which so-and-so is better will diminish.

5. It is possible, I suppose that I just happened to pick a Republican dyno while others have found Democratic dynos (the ones that tell you what you want to hear)!

6. Interestingly, the changes that have produced the most noticeable overall improvements in the car have been the anti-sway bars and the dealer provided TCM re-flash. The car handles and shifts a lot better than it did, although I am tempted to give at least a little credit for the improved shifting to the 10-wire grounding kit.

7. The car runs VERY well after all the mods. But, to be honest, it also ran very well when I bought it.


When I finally realized the paltry level of gains from bolt-ons, I did what many others do. I began to consider FI and did a fair amount of research into the options and potential problems. While respectfully recognizing that opinions vary widely on this subject, and I know that many folk are driving cars with FI, here’s what I’ve concluded based on input from the most knowledgeable people I could find (in contrast to my own wishful thinking):

A. G35 owners are essentially boxed in by the OEM design of the engine and transmission and overcoming these obstacles would require the expenditure of a great deal of money.

B. FI offers promise of short term success, but requires engine operation precariously near the brink of disaster and almost certainly will result in greatly shortened engine and transmission life. It is one thing to produce a 450 HP on a dyno for ten minutes and quite another to be able to drive a car around on an every day basis successfully.

C. Impressive dyno results and 1/4 mile times are published far more frequently than the problems and expenses incurred behind the scenes by those who have gone to forced induction.

D. Proper implementation of FI would require an expenditure of about $3500 to bullet-proof the tranny, $4000 - $5000 for pistons, rods and cams, and $5000 - $9000 for the increased air and fuel, depending on whether one chooses a supercharger or turbo. If my calculator is working correctly, this adds up to $13000 - $17000 up front or $11000 - $15000 later if you blow your engine.

BOTTOM LINE:

Don’t deceive yourself with inflated expectations regarding bolt-on mods. They don't do much.

Forced induction is VERY expensive if you do it right and VERY, VERY expensive if you don’t.

If I stumble on something I've missed or turn a 13.80 quarter, I'll re-post. But I'm not holding my breath!

 

Good post.
You summed up what I think many of us, to the advertisers dismay, have been thinking.
I know I for one have not been impressed with the hp gains the various bolt-ons have been realistically giving.
I think I'm going to start saving for a performane mod of a different kind. The V10 Viper!

In the mean time my Volks should be getting here tomorrow and will be going on the same time as my sway bars. [img]/w3timages/icons/smile.gif[/img]
So not all is lost for the advertisers in my case. [img]/w3timages/icons/tongue.gif[/img]



http://www.floridag35.com

 

I think that bolt-ons do offer enough added performance. My 6MT sedan pulled 248.11hp on a day where a stock coupe was doing 230hp and a stock (w/Z-Tube) 5AT sedan was doing 213hp.

Those numbers seem spot-on when comparing them to stock figures.

My sedan has a Stillen cat-back, TS ECU, Z-Tube, modified stock airbox (remove power duct, reseal to hood with foam tape, and remove lower resonator), and grounding wires (which smooth my idle, not add power).

Getting 248 over 213 seems like a decent power increase. The gap would be a little smaller if the stock sedan were a 6MT, but even then it'd still be about 30hp.

On the ECU, this is possibly the best upgrade I did to my car. There was another 6MT sedan there, which had the Stillen cat-back, Z-tube, and K&N filter that pulled 228.49. He went right before me (<10 mins) so conditions were basically identical.

The rev-limiter isn't the best part of the ECU. The A/F curve that my car has is VERY nice. It is everything they advertise - a flat line from 3k on to redline at 13.08 (tailpipe reading).

The remapped drive-by-wire system is also great. You can feel the quickened throttle response (although this might be all in my head. I'd have to try two cars blind in order to tell for sure).

Possibly the most important part is the advanced ignition timing. They advance it quite a bit, and my car needed higher than 91 octane to prevent detonation (I wish CA sold 93 octane). But aside from the ECU, the other sedan I was referencing is pretty much the same as mine. The ECU has to account for some of the 20hp difference between our two cars.

You're definitely right that the best bolt-ons are suspension pieces. Adding 30hp isn't going to shave time off your laps like a stiffer suspension or upgraded tires will.

Check the dyno day results at <a href="https://g35driver.com/forums/showflat.php?Cat=&Board=17&Number=323846&page=0&vi ew=collapsed&sb=5∂=">the NorCal section</a>

 

...and the new quote of the year goes to exagorazo, taking over DED's alien quote...

<blockquote><font class="small">In reply to:</font><hr>

5. It is possible, I suppose that I just happened to pick a Republican dyno while others have found Democratic dynos (the ones that tell you what you want to hear)!

<hr></blockquote>

Funny as funny gets!

The only thing I might add is that you neglected to add on the high flow cats and stick with the stock exhaust. If you could trade your borla for some high flow cats, I think the sound would be similar and your gains would definitely improve. Then again, the sedan is supposed to like the new exhaust, so who knows... This is why I've kind of lost the mod bug. I'm now starting to look at wheels and pimpinpearls stereo is looking pretty nice too. [img]/w3timages/icons/smile.gif[/img]


<font color=blue>The above statements are only my take on the issue. If you disagree with anything I typed then you are 100% right!</font color=blue>

 

I think doing the old intake and exhaust upgrade on these baby's is just the wrong way to go and I think there's a consenus of what some of the alternatives are: Plenum, Pulley and Plenum again. O and the Z tube. Or Free Tube as I have.

Many foks get most of the untapped Z power this way - add another 800-2,000 bucks for 10 MORE hp over what the plenum and pulley make and you'll prob have whatever there is to offer otherwise upto the NA limit. I think your observations are pretty well put and very much expected by some.

As far as the TS upgrade at higher rpm's I'm wondering what the plenum upgrade does in tandem with the 7100 rpm...anyone?

2003.5 DP 5AT Sedan
14.2 @ 97.18
Z-Tube
K&N Drop In & Airbox Mod
10 Wire Hyper-Ground
Crawford Plenum (V4)
UR Crank Pulley
Hotchkis Sways (M/M)
Polk EX-3500 Tweeters/Shock Sensor/H-Liner

 

Or you can drop about $1,500 for a completely failsafe nitrous kit and pull an extra 100 - 150 horses and a whole crap load of torque. I am waiting for all the people to tell me how bad nitrous is........................waiting......waiting.... .......I have only run it without issues on my last three cars and abused the crap out of them. Today, with A/F switches, RPM window switches, and progressive nitrous controllers. You get a pretty safe and healthy blast of power. You don't get it all the time (only 15secods or so bursts) and you have to refill the bottle, but then again who needs the extra 150 horses when they are driving to work. You only need when its time to embarrass people or your at the track. As for the bottle refilling, it does stink. I have no answers for that. I like the people who say, I'd rather have 10 - 30 extra natural horsepower so I can have it all the time. You can hardly notice 10 - 30 horsepower and will spend abou the same for my 150hp. Why spend all the money. Well let me take that back, because modding cars are still fun especially when you are doing the wrenching yourselves and you can hang out and enjoy the experience with friends. Anyway, enough of my BS, my point was that nitrous is not bunk, and it is safe, and it adds a lot of power. It may reduce the engine's lifespan, but if you own an infiniti your probably not the type of person to keep a car more than 3 - 5 years.

’03 G35S 6MT, black/black:
-Zex n20 Kit 150-shot & Bottle Opener
-Amsoil Air/Oil Filters & Oil
-Digital Nitrous Pressure Gauge & A/F Switch/Gauge
-Pressure-based Bottle Warmer
-MSD Window Switch

 

high flow cats are an absolute must for this car to make the most of the exhaust. test pipes are better but HF cats are a must.

you can't make power without noise, dude. a better flowing exhaust will almost always sound louder than a stock one. One thing you can do to mitigate the noise in the cabin is keep your revs above 2500 or so at all times. In town, drive around in 3rd or 4th gear to keep the revs up. The VQ has a drone at around 1800-2000 rpms from what I have seen. The fix is to keep it out of that range. in town I keep mine at 2200 and above. An exhaust can move that drone range around a little bit but not much.

a blower has always been the most cost efficient way to make power. and turbo's have always been the most cost efficient way to make power AND make torque.

nitrous, do it it is not scary (cept in a FWD car when it pulls the steering wheel out yo hand)

Better Life thru Chemistry
Black on Black 03.5 Sedan 6MT - Goodyear F1 GS-D3's 225/55/17, Custom Intake Tube, '03 "Z" Suspension, Magnaflow resonator, 6 Wire 4 Guage Grounding Kit

 

It seems that I've seen a few people here with coupes complain that the borla sounded too stock or too quiet and wanted to try something else, and I've now seen a couple in sedans say that they've had people complain that its too loud. Anyone know what's up with that?

 

The coupe in stock form is louder than the sedan in stock form. When you put an exhaust on the sedan, the difference in noise is much greater than when you put an exhaust on the coupe.

 

hey belerin, i'm not going to argue with you that nitrous, if used correctly, is one of the "best bang for the buck" mods you could do, but to what point? you brought up the point of refilling, but that in itself could get rather pricey, even if you're only squeezing at the most critical points. prices of nitrous per pound vary in different regions of the country. i feel sorry for the guy that has to pay upwards of $25 per lb. yech!

n1cK!

jUs' bE [img]/w3timages/icons/cool.gif[/img]

 

oh, and i must agree on that quote (#5), that was great! can't tell who's who, huh? ha ha ha! that was great!

n1cK!

jUs' bE [img]/w3timages/icons/cool.gif[/img]

 

If I were to spend money on mods, I would expect them to perform - not to only perform when I flick a switch cuz some subaru is next to me in traffic. Nitrous sounds like a great alternative for a young driver who needs to get into automobile fights. I'd rather have a car that performs consistently all day long.

 

Your car performs consistently all day long without nitrous. You ever race a 350z or a Subaru WRX. I have and beat them both without nitrous. If you are looking for a solid performer all around, then keep the car stock. Why futz around with it for only a little amount of horsepower if you don't intend to get into automobile fights or are worrying about racing other cars. Why spend all the $$$ if you only get a few horsepower and risk voiding warranty or just have an annoying exhaust sound. So if you want consitent performer, leave the car alone. If you are worried about being faster than other cars, really embarrass people with at large shot of nitrous. That is actually why I went with nitrous, because I do think the car is a excellent performer without mods. I only use the nitrous sparringly when I need to make a point.

For the other guy who was saying nitrous is $25 per pound. It's actually $25.00 per bottle ($2.50 per pound). Some places or a little more expensive like $3.00 per pound.

’03 G35S 6MT, black/black:
-Zex n20 Kit 150-shot & Bottle Opener
-Amsoil Air/Oil Filters & Oil
-Digital Nitrous Pressure Gauge & A/F Switch/Gauge
-Pressure-based Bottle Warmer
-MSD Window Switch

 

Buy the 100 pound [60 pound liquid] commerical bottles and local refilling equipment you can get it for $1.25 per pound. It will pay for itself in less than two year if you are a heavy user.

http://www.atlanticspeed.com/store/NOS%20Nitrous%
20Refill%20Station.asp

50 BHP per pound of N2O per 12 seconds

 

Very well written post, Exagorazo.

You basically summed up what is true for most modern
naturally aspirated cars. These cars come from the factory
well tuned, squeezing as much power as possible out of
the engine as is. It appears that the G35's design is very
efficient in terms of intake/exhaust and using aftermarket
pieces would only yield minimal results.

It will be interesting to see what Infiniti tweaks for the 2005
G35 to gain the extra HP. Perhaps that will shed light on
how to squeeze a little more HP out of the engine. If Infiniti
does any kind of internal engine change for the 2005, then
our bolt-on dreams will be trampled.