I recently installed several of the most common performance upgrades in my 00 V6 Xterra prior to doing so I had the truck Dyno tested at GRC for $65 they did three pulls giving a high of 120 hp at the rear wheels. Some may be surprised, as I was, with the low # but GRC assured me it was normal for actual hp at rear wheels to be 50 hp less than factory ratings.

Within 1 week I had a custom 2 1/2" cat back exhaust with flowmaster installed for $230 a stock replacement K&N airfilter $54 a computer upgrade from Jet performance in Huntington Beach California for $375 installed. I also went ahead with a full tune up and a new fuel filter as well.

Results where as follows. At first the Exhaust did nothing noticeable aside from giveing it a deep throaty sound at low RPM's and no noticeable difference at higher RPM's, however gas mileage did seem to increase by .5 gallon per mile (two tanks tested). After Installing the K&N filter I noticed a significant drop in performance and a 1 gallon per mile loss of gas mileage the only noticeable positive benefit came with the addition of a more aggressive sound from under the hood as you could clearly hear the air being sucked into the engine. Next the Chip, actually the stock ECU being reprogrammed for maximum performance. I was told it would take up to 3 days before I noticed any significant improvement in performance. In actuality the performance gains where immediately noticeable at the low end but not so higher in the curve. The ECU upgrade requires 91 octane fuel however it will run on 89 without pinging. As was suggested 3 days later there was a noticeable difference in acceleration and after shifting early for 3 days it was now shifting right at redline and pulling noticeably harder all the way through the RPM range. Still for days to come it seemed more performance gains where felt until now a week later everything seems to have settle into a routine. As for gas mileage at first I lost 2 miles per gallon but now I'm actually getting better mileage from stock by at least .5 miles per gallon. Now the bad news. After the tune up and a new Gas filter I noticed even more performance gains which indicates to me that the original Dyno could have scored better with a simple tune up. I have never been so impressed with the results of a tune up as I was this past week. I suspect my fuel filter may have been partialy clogged although prior to the tune up there was no reason to suspect I needed one.

I have not yet had the follow up dyno testing done but hope to soon. In my experience HP gains of 10 or less are nearly impossible to feal based on that information I will give you my best guess. I would be surprised if the actual HP gains from stock where less than 40HP with no loss of HP or Torque to be found anywhere along the RPM band. As soon as I get the actual results I will post them for everyone to see.

[This message was edited by Jimbob on 10-19-02 at 01:38 PM.]

That sounds pretty cool to me, maybe you should take out the k&n and put the stock filter back in if you still have it. I couldn't imagine a k&n drop in, exhaust, reprograming your computer, and a tune up giving you 40+ hp, however. Unless your truck was really messed up before the tune up. Get it re-dynoed and post the reports up on the web, that could be some real helpful information to some of the xterra owners on the bored if it turned out to be true.

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92 Pathy Se-v6
3in body lift
31x10.50

The loss in performance with the K&N was probably only on the low end and the ECU reprogram took care of that by better utilizing the increased air flow. I have no doubt that changeing back to the stock filter would likely decrease performance now that I have the ECU upgrade.

If you go by factory suggested HP gains I should be around 50hp better, thats 15 for the Exhaust 10 for the filter and 25 for the chip. I know these figures are inflated but the actual gains will no doubt be significant.

Just so you know a custom exhuast wont give you nearly as much gain as a tuned exhuast for the X. I had an HKSUV exhuast, K&N FIPK kit, Magnacore sparkplug wires and an MSD ignition. With those mods though we never got it dynoed I could easily spin 31 inch swampers (which in actuallity are almost 32 inches tall) standing stationary. When I just did the exhuast only it took a while for enough power to get to the rear wheels to spin them but with the mods I had as soon as i stepped on the gas the tires would spin. If you want more of a performance increase try doing SLR cams, and the large bore throttle body.

Scott "Chia" Holland

I went with the custom exhaust so I could re-route it for less exposure while wheeling.

The purpose of my post was to inform X owners of the ACTUAL gains from the most common performance mods. There are many opinions on which mods are better and which are worthless etc. etc. that's why a post with Dyno results has value. I personally disagree with your opinion of the tuned exhaust in many ways they're not actually tuned at all and I have read many articles stating that the large bore throttle bodies will not yield any performance gains. The cam would no doubt make the biggest difference but who wants to go there? Im not saying you don't know what your talking about you could very well be onto something but without dyno results we will never know.

I realize I have yet to post the finished numbers but that's not for lack of trying GRC is the only shop in my area with a dynometer and its hard to get time on it.


P.S. with our gearing and weight it would require nothing short of 300 ft pounds of torque to spin 32" tires on dry pavement and by doing so you would no doubt lose an axle or two in the process.

JimBob, did you take your Xterra out of 4-Lo? Joking!! Just, regular rule of thumb is you lose 15-20% HP through the drivetrain. Thus, 170HP at the crank (or flywheel) times 20% is 34hp, and that minus your stock HP(170) shouldn't be less than about 135-136 HP to the "Rear Wheels"(RWHP). Also, a great way to think about your engine is to think about it as a giant air pump. The easier it breathes, the more efficient and powerful it can become.

Later...

quote:

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Originally posted by Jimbob:
I went with the custom exhaust so I could re-route it for less exposure while wheeling.

The purpose of my post was to inform X owners of the ACTUAL gains from the most common performance mods. There are many opinions on which mods are better and which are worthless etc. etc. that's why a post with Dyno results has value. I personally disagree with your opinion of the tuned exhaust in many ways they're not actually tuned at all and I have read many articles stating that the large bore throttle bodies will not yield any performance gains. The cam would no doubt make the biggest difference but who wants to go there? Im not saying you don't know what your talking about you could very well be onto something but without dyno results we will never know.

I realize I have yet to post the finished numbers but that's not for lack of trying GRC is the only shop in my area with a dynometer and its hard to get time on it.


P.S. with our gearing and weight it would require nothing short of 300 ft pounds of torque to spin 32" tires on dry pavement and by doing so you would no doubt lose an axle or two in the process.

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Actually if you go to SLR's site they did do a dyno with the Open air intake, cam, large bore throttle, and gibson exhaust and a set of prototype headers and they had a 50 hp increase at the fly wheel.

Scott "Chia" Holland

Yeah I noticed the SLR information regarding thier performance upgrades but considered them useless since I would most likely never opt for the cam replacement.

quote:

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Originally posted by KDawg:
JimBob, did you take your Xterra out of 4-Lo? Joking!! Just, regular rule of thumb is you lose 15-20% HP through the drivetrain. Thus, 170HP at the crank (or flywheel) times 20% is 34hp, and that minus your stock HP(170) shouldn't be less than about 135-136 HP to the "Rear Wheels"(RWHP). Also, a great way to think about your engine is to think about it as a giant air pump. The easier it breathes, the more efficient and powerful it can become.

Later...

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The 120 dyno result I recieved was most likely a result of being out of tune, possible fuel filter or plugs but GRC does not subscribe to your formula they stated that the average drivetrain will eat "up to" 50 hp with an automatic transmission.

I understand the importance of airflow through an engine, in part that is why I dont believe in the so called "tuned exhaust".

prior to my Xterra my only experience with mechanical tinkering was with my 1970 buick GS wich was built and rebuilt by my hand several times. Of course my GS didn't have an over taxed computerized powerplant and amazingly it achieved about the same gas milliage as my X.

quote:

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Originally posted by Jimbob:

quote:

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Originally posted by KDawg:
JimBob, did you take your Xterra out of 4-Lo? Joking!! Just, regular rule of thumb is you lose 15-20% HP through the drivetrain. Thus, 170HP at the crank (or flywheel) times 20% is 34hp, and that minus your stock HP(170) shouldn't be less than about 135-136 HP to the "Rear Wheels"(RWHP). Also, a great way to think about your engine is to think about it as a giant air pump. The easier it breathes, the more efficient and powerful it can become.

Later...

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The 120 dyno result I recieved was most likely a result of being out of tune, possible fuel filter or plugs but GRC does not subscribe to your formula they stated that the average drivetrain will eat "up to" 50 hp with an automatic transmission.

I understand the importance of airflow through an engine, in part that is why I dont believe in the so called "tuned exhaust".

prior to my Xterra my only experience with mechanical tinkering was with my 1970 buick GS wich was built and rebuilt by my hand several times. Of course my GS didn't have an over taxed computerized powerplant and amazingly it achieved about the same gas milliage as my X.

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well since your 1970 buick GS is a little diff from cars today, a tuned exhaust on it wouldnt do anything. But on newer car with a computer a tuned exhuast can make much more of a difference. The computer can react badly if there is to much air leaving the vehicle.

Scott "Chia" Holland

Ah but you are missing something. I have the ECU upgrade its Jets stage II chip which meens it is "tuned" for my setup. Including my exhaust. Had I a "tuned exhaust" the chip would have likely been programmed differently and the end product would have likely been less HP.

A "tuned" exhaust is designed to maximize airflow against an engines need for backpressure. If you have a need for a tuned exhaust it is my oppinion none would be better than the factory exhaust.

Other bonuses to a custom exhaust are that you can route it as you please and it is welded not bolted to the cat which improves durability, something we can't have enough of off road.

Your numbers look reasonable for having the auto. My manual truck dyno'd at 133hp and 170ft-lb. Respective peaks were very close to advertised RPM.


...needs another axle to power, care to send me one?

120 to the wheels is not bad at all. You are at sea level so you numbers should be closer to the factory numbers measured at the crank. I bet my pathfinder would put down about 65 to the wheels here in Albuquerque, the altitude is a b!tch. 2003 Cobras that have 390 crank HP put down about 280 here. A 9 second mustang will make mid to high 500's. I tried my friends G-Tech and it said I have 49 HP. This is suppose to be WHP.

95 XE-V6 Pathfinder
Rancho 1.5 inch rear coils
Sway-A-Way torsion bars
Rancho RS9000's
2 inch body lift
32x11.5 BFG M/T's
15x8 AR-767