I dynoed after the Crawford and K/N Typhoon and lost 8 HP and 12 torque. Took them both off, sent the Crawford back for a refund, and went with a drop-in K/N and am happy with it ever since. Save your money for FI instead of tinkering with NA intake mods. I learned the hard way, at least no damage was done and only out a couple hundred bucks while learning.

 

What kind of cars do you guys have that DON'T like the added benefit of MORE AIR flowing into the engine??? Are these all on 5AT Sedans? Am I missing something here?

301-bhp!!! ...and growing!

 

Yeah, it does seem kind of weird that the plenum reduced power. I'm guessing that there are variables threw a wrench into things and altered the results either before or after (ie--defferent dyno, intake, uncorrected dyno readings, no ECU adaptation to the plenum, etc.)

'04 6MT coupe

 

Karlhungus- where did you lose it? low end, max, across the board?

'04 OB 6MT Coupe- Polished Vortech and Crawford Plenum, Kinetix Cats
'04 GSX-R 600

 

Lost torque across the board, and HP from 4K and up. Simply adding a CAI and plenum does not mean "more air". The VQ35 at 6500 RPM @90% VE only needs 400-450 CFM of flow. The stock intake can meet that easily with its open element design and smooth piping. The real restrictions start in the lower plenum, heads, and getting past the valves. The only way to make significant improvements in VE down there is FI, or very expensive porting, polishing,cams etc. which will only gain 40-50 HP at best. Stick with FI and an exhaust that will accomodate the added flow that will result. After that 100-130 HP boost, I would say you're done.

 

I have a 5AT and ran both the Injen and the Stock airbox with Z tube. BOTH are great with the plenum. I ran my 14.2 with the Injen. Give the car a couple days - reset the ecu right away and run it hard a few times. If the gaskets are sealed and the install isn't botched you should see a noticeable performance gain. 20 hp for $395 - who needs FI?

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

 

Where is everyone getting this "20 hp" from? One time for the record...

THE PLENUM DOES NOT GIVE YOU 20 HP!!!

Heck, even the manufacturer only claims 11rwhp at PEAK!!! I don't understand how you have some people claiming 20 hp, then you have other people claiming a loss of horsepower, all from THE SAME MOD!!!

I think I'm in the wrong forum. Does anyone know the web address to the G35driver technical forum?

301-bhp!!! ...and growing!

 

I heard it from the mouth of Doug Crawford and that was for the auto only. Sure he sells him but unless we have our own dyno proven numbers it's more hot air. He certainly could have been quoting Z results. The 6 speeds dont seem to respond to most mods with the same enthusiasm the 5ATs do. And while he quoted peak or best dyno - I dont care! The butt tells all and this butt is smiling..

Actually...looking at the chart from orlando dyno day the crawford folks clearly have at least a 10-15hp increase and the 20 I throw out there comes from the following analysis specifically:

In the first chart with the matrix of drivers - Take Driver #1 with the plenum, the Cats and Z tube and pop charger and compare to Driver # 4 who is stock. 16.7 diff at rear wheel right off of the chart. Now assuming Driver #1 had stock cats and NO pop charger the Hp # might go up by 4 or so and be exactly 20 higher than the stock #4 car.

11 hp seems like a low estimate from the looks of that very chart without much adjustment factor even though other mods get in the way (my sources tell me the pop charger and/or the cats are bad for HP tho) so 20 shouldn't be too much of a stretch for auto if one believes in these assumptions.



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

 

Your plenum (and subsequently the air traveling through it) doesn't know what kind of transmission you have.

I suspect it has more to do with one or more of the following:
1) Fuel maps
2) Octane availability (93 or 91)
3) Exhaust modifications
4) Air intake modifications

Something is going on between the above that totally screws over some cars with the plenum mod and transforms the rest into an F14.

After my install, the V5 beyond a shadow of a doubt made the car feel more responsive. In other words, it responded to the throttle in a more jerky, torquey way. However, using the G Tech it actually showed a consistent higher QM time, higher 0-60 and a lower HP reading. This was AFTER I controlled for temp, humidity, winds, pressure. I'm running 93 octane. I thought maybe that those on 91 were knocking sooner with the plenum perhaps, I don't know. Doug and I discussed this for a half an hour and had all kinds of theories but until someone learns more about the G's fuel maps we couldn't conclude anything. His experience is mainly with the Z which he says has more fuel maps than the G.

Since that dismal test, I have reset the ECU. Believe it or not, the shifts felt different, touchier, more responsive. The idle became squirelly for a while.

I haven't retested yet since the ECU reset but will this weekend.

Another poster mentioned volumetric efficiency, but what that poster failed to cite was evidence that the front two cylinders experienced the same VE as the remaining 4. I'd also like that poster to explain why Neff then picked up 16 HP from an R/T Cat if it's true that the plenum mod does nothing. I supsect that the front two cylinders experience a slightly less VE than the others.

There seems to be proof on both sides that the plenum can use it's power for good and evil, and I'd sure like to get to the bottom of why.

2004.5 Coupe/5AT/Ivory/Everything but front spoiler/Nismo CAI/Crawford V5

 

6-5,

For the record...
1. I am driver number one! Driver #4 is a very good friend of mine, his name is Ian (Demonteverde).
2. I recorded all of the data and wrote the write up on the dyno day event!
3. I planned, scheduled and orchestrated the entire event.
4. I installed most of my own mods and understand what does what in regards to gaining hp.

...and you're using my own data against my own statements????? WTF?????

No way possible the Crawford Plenum alone will yield a true 20 bhp on any stock VQ35DE. The RT Cats and intake helped TREMENDOUSLY in the "net result" of getting air into and out of my engine more efficiently. You're correct, the dyno on Crawfordzcar.com's website is for a 350Z but it does not show 20 bhp (17rwhp) anywhere. Doug himself states that the Crawford Plenum provides more hp COMBINED with the Crawford Cats than with the stock cats. The RT Cats (which are on my car) are more free-flowing than the Crawford's so how could this have hurt car one (ME)?

This kind of stuff drives me nuts. I really try not to spread MISINFORMATION, but please don't use countless hours of my own hard work to try to "fabricate" hp claims. The goal of the Central Florida Dyno Day write-up was to let people see different G35's in various states of tune (reads with different mods) so you can see how these mods work together. Let's use the data for that purpose and that purpose only, please...

...and incase you're wondering, Yes I took your post personal, because I put a lot of effort into obtaining all of the data and posting it to help people like yourself and it appears that you're trying to use the data to make stuff up. The whole point of posting the data was to keep people from having to make stuff up, get it?

301-bhp!!! ...and growing!

 

Well said Neff. Everybody has their own experience and opinions based on that experience. That said, it is clear that the plenum does "something", but it is highly dependent on the other installed mods. Surprise, surprise.

Since a modern engine is a very complex SYSTEM, changing a major part of that system, namely the dynamics of the upper intake (volume, velocity, harmonics) is usually not ECU-friendly and needs to be fully understood. This understanding is beyond most bolt-on tuners using "average" fuel/air ratios from a dyno.

I also take issue with the whole front 2 cylinders gasping for air myth. Do we really believe flow-bench numbers that do not take into account the dynamic compression/decompression of the plenum? Intake charges are pulsed, with waves, reflections, and harmonics that affect flow. Feel free to flame, but its my opinion that a couple of guys in Nashville, while great to deal with and mean well, with a flow bench and a torch have not solved anything.

Also, do we really believe that Nissan would have intentionally allowed 33% of the engine to operate in an over-rich condition especially in this pollution controlled environment? That plenum was sloped for a reason and its not to clear the damn hood. It is sloped to maintain velocity and reduce the amplitude of the standing waves accumulating at the wavefront. Ever wonder why supersonic aircraft have pointed noses and V-swept wings? By removing the slope, you have created a big fat wall for ocillations to bounce back and create turbulence. You guys can do whatever you like, but not on my VQ.

Get a TT or blower at 6PSI and you will have HUGE gains NOW instead of marginally noticable or negative results for your money. All I'm saying is if you're going to mod, go for something thats going to make you crap your pants after you pick it up. Then the debate about 11 HP here, 20 HP there will seem stupid.

 

karlhungus,
I appreciate your input and it seems reasoned. But how do you explain Neff's 16 HP increase? The cats alone couldn't have done it. The cats and Pop charger couldn't do it. The plenum seems to have had to have done something.

2004.5 Coupe/5AT/Ivory/Everything but front spoiler/Nismo CAI/Crawford V5

 

fish,

I dont know. But from what I've read, it was 1 data point on his car. I was skeptical as soon as I saw the plenum, but I bought into the hype and had to give it a go. I was so pissed when my after-plenum dyno showed a loss, that I waited a week after ECU reset and paid another $90 to have it done again to be sure. And it was repeatable, worse actually. I would be interested to see if Neff still has his gains or if his ECU has already "tuned it out".

See, what people dont understand is that even something as simple as installing a spacer (Esprit) between the upper and lower plenum (to thermally isolate and increase volume) can have a negative affect. Why? Because by decreasing the temperature (increasing air density), you have effectively increased your compression ratio. This is usually a good thing. But since the ECU thinks it knows what the effective ratio should be based on incoming air temp and engine temp (coolant temp), it sets the timing accordingly. So when small pinging (from increased compression ratio), imperceptible to the driver, are detected by the sensors, the ECU is surprised and does the "safe" thing by retarding the timing. This effectively negates or more than negates any gain the enthusiast hoped to make. Unless he wants to run premium for $2.70/gallon to get his gains back. It is folly to mod without a reflash as the final fantasy, the ECU knows all.

 

You guys also have to remember that different G's put out different power to the wheels straight from the factory. One could have a particularly strong engine while another can be weak.

The only thing that can be said with any kind of certainty is that there are too many variables in the car (from everything from the wheels, to tire pressure, to how dirty the filter(s) are), dyno equipment, environmental conditions, etc. to compare 1 car to another.

 

Just to clear something up... I had the Crawford Plenum on my car for 2-3 months before the dyno day. I had the Z-Tube on for the duration that I've owned the car (well since ~900-ish miles), and the RT Cats right after break-in (1 week later). My cars ECU has long ago learned whatever it needed to get me long lasting ECU data, and has incorporated these changes in the fuel maps and/or where ever else it needs to by now. The dyno did not read something that was not there. The 16.7 rwhp that I picked up as a result of these 4 mods SHOULD make sense. They are backed by the manufacturers, ricer math does not prevail, normal engine tolerances should not swing by 5% (come on people, haven't you heard of precision machining?), etc... The results of the dyno day show that similar mods produce similar gains on similar cars with relatively similar conditions. This data doesn't appear to be flawed, so how can we disregard the gains showed by "BALANCING THE EQUATION". Meaning, if you allow more air into an engine and then allow the same air to flow out of the engine more freely, you will gain more horsepower.

Another point... The same morning that I installed the plenum (already having the RT Cats and Z-Tube, P/C) I instantly felt more wheel spin between the gears. I also noticed more throttle response, and for the first time I could honestly say that the butt dyno came alive. I intentionally did not spew out nonsensical horsepower numbers in public forums, but something definitely registered on the butt-o-meter and I posted just that. Since that time, I can honestly say that I have not felt a drop off in performance (nor an increase). I have gone to the track and beat a stock 2003 G35 5AT in the quarter mile (and I am NOT a good drag racer). The stock 5AT was Dabomb and he actually had me at the 1/8 mile point, but the mods kicked in and I took him by the quarter mile. Just reeled in the little fishy [img]/w3timages/icons/tongue.gif[/img].

I guess people will have different experiences with the same products, but for me to sit back and read posts that say people are not satisfied with the plenum, can I suggest you look into the other side of the equation before jumping to any rash conclusions. Try changing out your exhaust or cats for some used straight pipes (might cost $100). Or buy some used high flow cats for a little more. Look into a y-pipe or a TD exhaust. Something to help "balance the equation".

Good Luck.

301-bhp!!! ...and growing!