Thanks for answering all my questions. After the additional information you've given me, I have come to my own conclusions but not to the contrary. It would be a good day to have a VQ if every mod produced this type of result.

Going from stock to these headers would be interesting to see now.

I'd like to thank you again for going to the trouble to do all this. I know the direction I'm going now.

It does seem that way...especially since Semtex has about almost all the bolt ons to go N/A for this car as possible.

You know what kinda confuses me though? This car has made more power before. I dyno'd after the underdrive pulley went on, back in May of '09. Check it out. I hit 330whp. This either shows how finicky dynos can be. Or it shows that my car has lost power as it's broken in, had more miles put on, etc. But I only now have 10,500 miles! So it's not like it's all worn or anything.

http://www.the370z.com/members/semte...ced-052009.jpg

^^^^Hmmmmm....This is a very interesting point Semtex

Dirty filter(s) on the intake?
Different variables (weather, how warm the car was, etc.)?

Did you change your wheels and tires between the runs? Differences in wheel dimension could be the cause because of this. When trying to research how to compute exact optimal rpm shift points using dyno runs and gear ratios, it was mentioned that changes in the wheel diameter and the contact surface area could affect the dyno data results.

http://www.datsuns.com/Tech/torquehp.htm
http://www.datsuns.com/Tech/whentoshift.htm

No.
Maybe.

No.

price range?

What?

Pricing info is in original thread here: http://www.the370z.com/intake-exhaus...ders-here.html

Well, now there is more info to examine. Dyno's can be very "finicky" as you put it. If set up right, they can be very accurate, but if one input parameter is off just a little the hp and torque numbers will be off. Good dyno operators can get your car to read any number you want, of course there is no benefit in that.

My rear tires are worn down to the wear bars. (In fact, I just ordered a new set of Michelin PS2s.) I wonder if that might have affected the dyno numbers, as the diameter and overall circumference of the tire diminishes as it wears.

Michelin PS2s = BALLER :eek:

Ben, I like the results. However I just HAVE to make one comment. When I installed headers and hfc's waay back when, I know I lost a bit of torque from it and gained not too much power. Now this FI LTH loses a little power and gains a little torque back. So I HAVE to ask, what do you think would happen if you threw on the stock headers at this point. Would it make the same figures as your FI LTH? It has always made me a little curious if I would get all my lost torque back and maybe lose some top end hp if I installed the stockers back on... I don't know if headers have been a worthwhile investment on the car thus far. Maybe with forced induction since more flow = more power... but my opinion of it is rather mixed thus far. Just a thought, not trying to undermine FI's product or Stillen's...

That's exactly what I was wondering. Since it was always the same shop that you dynoed at, would they be able to do overlay of the FI LTH graph with the stock header graph so you could see the difference?

That's a good question, and to be honest I'm not 100% sure. I'm inclined to say that I would have regained the lost low-end torque if I had simply thrown the stock headers back on, but I don't think I would have gained in the mid-range the way I did from the LTH.

Here is the torque chart from way back when I put on the Stillen headers.
http://www.the370z.com/members/semte...9-042209tq.jpg

You can see a pretty sizeable loss of tq all the way up to around 5250rpm. Now, one thing to note about this chart above is that Sharif was having an issue with a software update from Dyno Dynamics at the time, and as a result was only able to display the tq units over on the right-side Y-axis in Nm rather than ft-lbs. As I note right on the graph, ft-lbs. are smaller than Nm; 1Nm = 0.737ft-lbs. What this means is that the delta we see between the torque curves is somewhat exaggerated -- the gaps are not really as large as they visually appear to be. And all this of course makes it all the more difficult to compare to the latest graph, which displayed torque in the correct units of measure:

http://www.the370z.com/members/semte...2310-sheet.jpg

So what can we conclude? Well, due to the difference in units of measure, I think we need to set aside the question of whether the magnitude of the gain from the LTH matches -- or even exceeds -- the magnitude of the loss from the Stillen headers. I mean, I suppose I could break out the calculator and do a point by point conversion of the Nm curve into ft-lbs., but I don't really have the time or energy right now. I *think* my gain from the LTH exceeds the loss from the Stillen headers, which would mean I have a net gain over stock, but I'm not sure. Having said aside the magnitude question (at least for the time being), I do think we can at least observe that, whereas the loss in tq from the Stillen headers peters out at around 5500rpm, the gain in tq from the LTH continues all the way up to about 6900rpm. So we definitely have a legit gain in tq from 5500-6900rpm. And setting all of that aside, at a bare minimum we have pretty significant weight savings over stock, which we'd obviously lose if we were to simply throw the stock manifold back on.

We also need to look at HP. Disregard the apparent gain from 306 to 317 shown in the graph above. It was later determined that the 306 baseline was messed up because they didn't pull all the way to redline. For all intents and purposes the Stillen headers yielded no change in HP. Maybe +1 or 2 on the top end at most. But look at the HP gain from the LTH. If there was no HP gain between the stock headers and the Stillen headers, yet we're seeing a real HP gain going from the Stillens to the LTH, then we can deduce that this gain would equally apply over the stock manifold.

The HP gain is pretty much across the board. The only place it falls short is at the peak, 7300rpm and above. Which brings me to my next observation. When Tony tested his LTH, he tested it against a car running the stock manifold and his HFCs. Check out his gains:

http://i371.photobucket.com/albums/o...er_SAEcopy.jpg

What's the difference? Well, part of it, obviously, is that his baseline ran the stock manifold whereas mine was with the Stillen header. But we can already see from above that the delta between the stock and Stillen headers is marginal for tq, and non-existent for hp. So that's not it. Okay, my baseline was with Berk HFC while Tony's was with his F.I. HFC. Well, I'm sure there are some differences, but I can't believe that Tony's HFC is so much more restrictive than Berk that it would account for such a big difference in gains from the LTH (which deletes the HFC).

That leaves just one other factor, doesn't it? Tony is running his F.I. CBE, while I'm still running Stillen's. Tony and I have actually discussed all this, and our working theory right now is that the Stillen CBE is holding my car back. Tony thinks that there's now too much flow with the LTH for the Stillen CBE to handle, so the CBE is bottlenecking the flow. And I have to say, based on the process of elimination I just took us through above, I don't see a more logical conclusion. Indeed, notice the similarities between Tony's graph and mine. Both show the same pattern of a large jump in TQ on the low end, followed by a convergence of the lines right at around 4k rpm, and then divergence after that. The big difference is in what happens after that. On Tony's graph, the two lines continue to diverge in an ever widening path, i.e., his rate or magnitude of gain increases as rpm goes up. But with my graph, the gap stays pretty much constant from 5k to 6200k, where it then changes direction and eventually crosses over at around 7k and actually dips down below the baseline shortly thereafter. Hmm . . . it's as if the system runs out of breath at the final stretch, isn't it?

And that's why I now have the F.I. CBE on order (12" resonators w/ CF mufflers). And of course, I plan to do a before and after dyno just like I did with the LTH so we can have objective data to tell us for sure. It will essentially be a showdown between the Stillen and F.I. CBEs. This is what I expect the results to be: we already know that F.I.'s CBE makes more power over Stillen's, but up until now, the advantage has been somewhat marginal, IMO. Certainly not enough for me to justify the expense of laying out the money for an F.I. exhaust. But the comparison numbers we have (from Tony) to this point between these two CBEs is from a car equipped with stock manifolds and stock cats (I think F.I.'s advantage with everything else stock is only like +1 or 2whp if I remember correctly).

I believe the LTH is the game changer. Once you uncork everything with the LTH, suddenly the difference in gain between the two CBEs becomes magnified. That's the working theory. The dyno results will tell us if we (Tony and I) are correct or not.

Such an overlay wouldn't be a valid comparison, because so much time elapsed between when I had the stock manifold and now. Too many conditions will have changed for it to be a valid apples to apples comparison.

Nice write-up! Lets see if your theory is correct.

What mods were on the car for this dyno run?

Everything. It was right after I installed the underdrive pulley. So it already had the CBE, intakes, Stillen headers and Berk HFCs. The only thing I didn't have yet was the Uprev tune.

I'm wondering if the worn tires have something to do with the diminished dyno numbers. Because tire wear means the overall circumference of the tire gets smaller over time. And if I'm thinking this through correctly, a smaller circumference tire would spin the dyno drum less, thereby resulting in a lower number. Someone tell me if that's logical or if I'm completely off base, lol.

Your tire diameter changed by as much as 3%, but the dyno is measuring how much load you are putting on the drum, not how fast you are spinning it overall. Effectively it is a gearing change, so you've gone from a 3.69 to a 3.83 final drive (worst case). Some dyno's are more finicky about this than others so there is a possibility of a small margin of error.

If the tire diameter did change, it would error in the way of better numbers I believe (that's if it showed up at all).

I'm still new to the six cylinder import cars, but I've worked with American V8's all my life. Every time we've opened up the exhaust to a free flowing setup without changing anything else, we've lost torque and gained horsepower. The exception being, the exhaust starting out really really restrictive to begin with, in which case we gained both hp and torque.

As a rule of thumb, shorty headers were better than stock manifolds and would help keep the torque down low and increase hp up high. Full length headers would give you even more hp up high but would sacrific torque down low. Removing the cats usually resulted in the same as going to FLH. FLH's really start to come alive when you start going with a more agressive cam or forced induction. Primary size is usually the most important factor in any header. Too small and you're not able to flow enough air. Too big and you loose all your velocity and ability to scavange.

Another question I have for someone that really knows these cars, how do the "adaptives" work for these VQ's? Can I "reset" the computer, and if so what does that do? Are there a number of parameters that the computer "learns" over time.

In cars I've worked on in the past, it takes a few hundred miles to get the adaptives set to where they are really happy.

True but the hp/tq curves will not change...the numbers might vary a bit. You could use that arguement for any dyno that was not done on the same day including the Stillen/FI comparison...so why not compare the stock vs FI? No big deal though, good write up

Well, post 96 above shows my tq curve from before the Stillen header install. Give my analysis in that post a quick read if you haven't already and tell me if you think it makes sense.

Damn this does not bode well for Stillen CBE's if that is indeed the case. First off kudos to semtex and Tony for the in depth analysis, its great how these guys will go to great lengths to show us what the "real" pros and cons are. Semtex are you planning on going with an FI CBE? I hope if you do that you see the gains you were expecting to see though in reality how often are you going to be constantly that high in the power band. Keep it up man.

Per the last two paragraphs of post 96:

Also, my expectation is that the gains with the F.I. CBE vs. Stillen's will be across the board, not just in the top end. But we will find out for sure soon enough.

Hey do you have a CEL?

No. I never had a single CEL with the HFCs and I think it's even of less likely that I'll ever get one with these, given the design of the O2 sensor ports.

im in Ontario, i think they run the car at a steady speed on a dyno and shove a device up the tailpipe. so probably would fail if this is the sniffer u were talking about.

HFC's will often pass the sniff test, test pipes (or LTH) won't.

Won't pass sniffer with LTC/test pipes. Definitely won't pass under load (dyno).

You let them rectally violate your Z!?!?! :wtf: :shakes head:

haha its either that or dont drive it at all. pick one bud :p

I really think someone should lend semtex a FI exhaust. Afterall, his contribution to this fourm is quite significant. It would suck if the 1.5k FI exhaust is not any better than the stillen's.

He can always just sell it for a marginal loss anyway, not a big deal if he has the disposable income. Also, I just noticed the "Tags" at the bottom of the page for this thread: "fast intentions, long-tube headers, semtex, yiffing, yo dawg"

Yiffing? What the hell? lol

Yiffing is where it's at :twocents:

Just make sure you use the right lube prior to insertion. Just think, you know all those tedious oil threads? We could start a "What's the best lube for my tail?" thread. ;)

Actually, I just got laid off. I'm out of work as of 5/21, so disposable income isn't what it used to be. Oh well, c'est la vie. :icon23:

Anyway, I appreciate the sentiment that Kevin expresses above, but I'll be fine. I knew the layoff was coming prior to ordering the F.I. CBE. I was able to sell my HFCs and Stillen headers, which goes torwards the F.I. Plus I'll probably be able to sell my Stillen CBE after I make the switch, which will further help me recoup my investment. So no worries.

send semtex money via my paypal account @ stephenhumby@hotmail.com.



lol