A well designed full length header/collector setup will help your lower and upper numbers. But most of the time you are you are correct.

 

I'd like to have dynojet themselves explain why I couldn't get good dyno results in 5th at less than 2k. Not saying it's not a possible thing, I want to hear their explanation and if they agree with you.

Let's draw a line between member's here that are chasing peak numbers and those of use that want better hp numbers but want to see the science of low end torque preservation applied. Yes, duing the whole 10% of the time my engine is running in "race" mode during it's life time, I won't be seeing rpm's less than what,........ 2.8K or so. I'm wanting to preserve as much low end torque as possible for the other 90% of the time when I don't any need or interest to abuse the engine with rpms and WOT. I'm tempted to do that enough as it is. I don't want a powerband that forces me to rev more to get satisfactory power delivery. I'm willing to take some loss in low end, but I have to have dyno's that reveal what's going on at less than 3k to know if that has or has not happened.

Now, again, for those members that drive in a manner where they won't see less then 3k very offten, I don't feel they have the reason to care like I do, fine. When I drive my car I'm either real easy on it shifting out at around 2.5K into the next gear or I'm making a all out attack. So I DO want both, lowend and a high end. Thus far my current mod's have kept me their, IMO.

 

Starting a pull down that low in the 1:1 gear really loads the engine. On my LS1 I've never had a operator start a pull below 2K. I don't think a chassis dyno would show much of a change down low in the 1:1 gear. The engine would be sluggish and the air velocity in the intake system would be killing any gains the headers could be giving.

Would be interesting to see some graphs of Header A vs Header B in like first or second gear from down low. But then most people would complain about the numbers are screwed up vice just looking at the difference between the two sets of numbers.

Also on a Dynojet you can print out the run in column format and it gives you Max, Min and Avg numbers for a run. Then with the AVG numbers you can really see if there is any overall gain from a part/tuning.

It was said before, we buy HP, but drive TQ.

 

TQ gains are more important for us 5AT owners who can not increase the RPMs from launch or between shifts. I have avoided test pipes at this point because I am afraid I will lose too much TQ at low RPMs. I have considered a pulley set and a Technosquare ECU to possibly help tune the system, but would rather wait for a better solution that will allow for more control and tuning without sending in the ECU. The quickest gain is obviously a SC setup but I want to give that some time to play out as well. Another alternative would be cams, but pricey to have installed. NOS is another option, but I do not want a bottle taking up my hatch area. Maybe someday there will be a torque converter for us, but not at this time that I know of.

 

Hello,

We dynoed our XERD headers on a stock 6-speed 350Z, no tuning involved. We put the car on the dyno and that was it. The reason we dyno all of cars this way is to actually show the customer what realistic power he can expect, not just when the car is cooled down or tuned.

Our dyno results showed 17hp and 3tq gain over stock with just a simple bolt on and no tuning involved.

The reason we only gained 3 pounds of torque is because with our header design it changes the characteristics of the car which is not tuned to handle such a product from the factory. The air/fuel ratio doesn't automatically adjusts itself for maximum performance and this is where a S-AFC or any other air/fuel controller comes into play. Our headers design requires tuning in order to achieve the most horsepower and torque, that is really where our product shines. Without any tuning it is still one of the most impressive headers on the market for the 350Z.

We will be getting our test car back in about a month and then start playing around and doing some tuning and show the new results. We expect mid 20hp and between 10-15tq at the wheels realistically but the dyno results will do the talking for us.

The HP and TQ figure we advertise are real gains in normal driving conditions which means that every single person who will use our parts should see very close gains as well, give or take a few. What we advertise is what you get, with a little more tuning you can achieve a lot more.

BTW, the automatic 350Z should show better dyno results, it might show lower overall numbers compared to a 6-speed 350Z but the gains from the headers should show a bigger gain.

If anyone has anymore questions about our products feel free to contact me at 818-889-3737 or by E-mail: sales@xerd.com

Thank you very much. Eyal

 

I am in agreement with you guys. Please see my previous post where I stated...

"...Even if you did lose bottom end, I don't think it should be a big concern since you'll only be affected by it in 1st gear, whereas you'll reap the benefit on the top end in every gear."

None-the-less, most people won't want to see a big loss below 3k with headers. I'm not stating that all headers will do this, but merely that it's likely if the diameter is too large, the exhaust velocity will drop and a loss in low end torque will result. Take a look at my dyno with test pipes installed and you'll see what I mean.



As you can see, by installing these pipes, I lost torque from 1800 to 2800rpm. I was more than willing to give up the bottom end to gain the midrange and top end, where I also spend most of my time. I am just curious to see the bottom end with their headers to see if they have a dip in torque as in my graph above.

 

350Z 2+2 ???,

I will try to take a picture of the dyno sheet tomorrow and post it on here. From what i remember we didnt lose any hp or tq at any point in the RPM's.

Thanx, Eyal

 

I'm not quite following this. Why would the gear your in make any difference in air velocity in the intake? Isn't that completely dependent on RPM and throttle position? In other words, if you go WOT at 2000 RPM, won't you have the same airflow regardless of gear?

Not saying you're wrong at all. Just trying to understand that statement.

 

Think about trying to take off on the street in your 1:1 gear. Would the engine be able to rev as freely as in 1st or second? With the engine seeing a rather huge load placed on it won't be able to rev up like normal. The engine would be working outside it's normal parameter at that point. The Volumetric Efficiency would be way down. Then the data you get from a dyno would not be something you would see in the real world, cause the engine would never be operated in that area of the VE table in the PCM or ECU or what ever Nissan calls the engine computer.

There might not be any change or so small not worth talking about. A change of 1 or 2 rwhp or tq is really nothing on a graph, it's less than 1% of the engine's output. That could be nothing more than the engine coming to temp or how long it had been waiting to go on the dyno, fresh off the street vice sitting overnight and the transmission and rear end is at ambient air temp. Or even some like changing the oil to a lower grade. Or it could be just how the dyno reads on that pull.