You're basically answering your own question The stock manifold is good for low and mid range power, over 5000rpm, VE (and directly related, torque) quickly drops down. By reducing the runner length by 10cm and improving the overall design, the VE curve is pushed upwards within the rpm range. Engines running uprated turbo's and cams will have a more useable and less peaky power band with an intake manifold that performs best at the same rpm's. Compressor efficiency is key to good power on a turbocharged engine. Apart from that, the stock manifold has lots of flaws, like the ignition coil 'incisions' or the kinked, small entry for the 6th cylinder. I notice people on the worldwide 300zx forums claim that the stock manifold is the best, but noone ever tested it against other custom manifolds. Looks like I'm the pioneer here I make these manifolds for research means and if proven effective, they'll be for sale as well.
Have you flow tested these and do you have results? Im not calling bullshit on your product btw, just curious to see some stats.
Tony, KK. Rutger. True on every point but gains, I predict will be incremental at best. Particularly on a boosted engine!!! Yep, the stock manifold does have concessions made with regards to manufacturing/commercial influences, but in reality, these imperfections are largely noticed naturally aspirated. Gasflow under pressure, and in particular, accoustic influences which is largely what youre exploiting here, can be asked to do some much more difficult stuff with minimal losses over what is accepted as ideal. Im predicting this setup will show far greater gains in an NA installation than a tuned up boosted setup. However, subjective dyno pulling will reveal all. Above all, I admire your clobber m8 and am far from criticizing it. Now, stop buggerising around on forums and get back to work!!!!!!! E
Flow benches are usually used to find dead spots in heads. They're of little use in a manifold as the total wave resonance effects are very important here. The only people who can measure those are a handful of engineers at some high universities and car manufacturers. It's much cheaper to dyno the engine. This man explains it best: http://rehermorrison.com/tech-talk-70-airflow-fallacies-avoiding-the-pitfalls-of-the-flow-bench/
Well it's just past midnight here, not gonna upset the neighbours with a noisy milling machine. Still got some work left to do before it's dyno time. The laws of airflow physics apply the same to turbocharged engine as naturally aspirated. The turbo just puts pressure upon the air the engine consumes. The difference can be there though. But this only applies when the compressor is placed directly against the manifold, disturbing the waves and taking a beating from them itself as well. This why engines with the compressor against the intake (such as cheap turbodiesel engines) use short non-tuned runners, and very short camshaft profiles.
Rutger, thanks for your informative answers, and explaining it in English and not scientific babble. Helping me so much to understand this subject of manifolds, airflow, and effect on performance. Looking forward to the dyno results for the comparison.
Flow test, dyno, whatever your testing poison may be Have you done any back to back dyno work, id love to see a run comparison? Cheers for the update.
After testing this manifold the car will be rebuild to OEM configuration and tested a third and last time. This way the dyno curves can be compared. This wil be the last update with no vid of the car running. I'm almost done now. I quit my job today (being tired of working with a bunch of bitches) and have 6 weeks of free hours left on my contract so it's gonna be late this week or early next week that the car will run with this setup. I choose not use the factory idle outlet on the pipe coming from the turbo. Instead, I welded a new pipe to the hardpipe just in front of the TB. Why you may ask? Well, the intercooler provides flow resistance, so part of the air finds a faster way through the idle system heating up the engine's intake air. It also loads that turbo different to the other. The effect is small but for the amount of work (just a new pipe welded on) it's well worth it. The valve covers were modified in the same way as the ITB manifold, with the vent guide plates modified and refitted. The oil filler is custom, just a simple design. The fuel system is almost done, and very similar to the ITB setup. The ends of the OEM fuel rails are cut off and replaced with bungs, were the copper lines can bolt into. Left to do is the vacuum stuff for the brake and clutch booster, and some other small hose connections. After that, the manifold can be welded shut (is still open at the lower side).
Got the engine up and running. Apart from a gasket leak all went quite well. Requires just a bit of work but for now it runs nice. The only thing I can't get my head around is a very strong suction sound coming from the manifold, seems to come from the center of it. But I can't find any leaks, and with a leak big enough to create such a sound the engine couldn't idle as it does. The only thing I can think of is that the changes I've made to the idle system increase the noise. It's not audible in the vid but if it goes on like this I'll try to capture the sound. Should be seeing the dyno soon. Nothing spectacular, just evidence of being in working order http://www.youtube.com/watch?v=EWiRPKd_lsE
I got to the dyno last week, but due to a blown fuse the dyno itself didn't work. So in the meantime I replaced a couple of small things (injector plugs and seals) and went back today. First result was a disappointing 236,5hp at the wheels. But for some reason the AFR's were extremely rich (see the dyno sheet) so I pulled and plugged the FPR hose and power rose to 253hp ATW with lowered AFR. The AFR was still to rich, we estimated the engine would do around 265hp ATW with the right AFR. That's very close to the ITB setup at 263hp ATW, but that run was done when the temps were much higher and I used slightly less quality fuel. So I'm quite satisfied with the result. I still feel some air leak is causing the engine to run to rich, but as I can't find it there could also be something wrong with the AFM. Now it's time to swap the stocker back in and dyno it... Blue is ITB's, green the run with this manifold and red the run with to much fuel. http://youtu.be/FXhDmrgMzL4
Nice to see the dyno results. Thanks. That's a very smooth power curve, actually is fairly straight till the top end. Regards to the "air leak", maybe your new plenum just sucks. (pun) Seriously, love your work and the engineering behind it. Well done.
Did you do a base dyno run stock before any mods? Would have been good to do this before and after for confirmation of the results.
he said his going to put the stock manifold back on and rerun im curious to see.. technically the stock mani should see a steeper jump in power at the beginning as it was theoretically designed for low down torque but im curious as to how much this would actually be on a graph in a fully functioning car
Yep but it's always best when tuning or testing new parts to do a base run first, then test/tune new parts, then restore back to the base config and do another base run. This helps to rule out or identify any environmental changes that may have affected the results for the new parts.
I wasn't able to do a base run cause when I got the car too much was wrong with it. Required a plenum pull to start from. The engine performance will be much better now that I've replaced parts of the harness and PTU. If dyno'd the first time with the stock manifold it would probably have made 200hp ATW at best The car will soon be rebuild to the stock manifold, I'm not so much interested in the maximum power but more in the actual shape of the HP curve. If this and the ITB manifold clearly hold more power in the higher end I'll be happy with it. Note that this is bone stock ecu and has not been tuned to the difference in torque output over the rev range. In theory, the stock manifold may give similar maximum output, but with an ignition and fuel tune on the custom manifolds they should perform better.
That's what I'd be keen to see as well, the stock manifold overlayed against the custom manifolds just with the stock ecu. Then put in an aftermarket ecu or nistune and tune it up. The curve on the two custom manifolds is almost identical, just with different power outputs. Will be more interesting to see how the curve on the stock manifold differs, rather than peak power.
I am with GMbrezzo here I pick its to do with the Trumpets and your intake design - most likely velocity of air and volume of air in the plenum as well, I dont know enough about fluid dynamics to get any more detailed, but I always thought of the plenum acting like an airbox on a CV carb and when you remove the air box on a CV carby it presents like you have here - a lot of sucking sounds (yea its a carby so that goes anyway) and running rich. I pick your plenum is slowing down the air flow velocity once its entered the main part after the throttle body and creating turbulence as it tries to get into the trumpets. again this is just a guess.
I managed to get the car back to stock, easier said than done. During the assembly I somehow managed to make a stupid mistake, the injector plug for cylinder 4 didn't secure well, skipping the 4th cylinder for a few km's. I checked every plug twice but this one somehow skipped. Also, after a test drive the 6th cylinder went dead as well, and the 1st injector leaked towards the upper side of the fuel rail, I should be lucky it didn't get worse and the car didn't burn down. The cause of this is the incorrect fit of the 'Buna' fuel injector seals I bought through CZP. They're way to thick and I could barely fit the injectors into their rails. So injector 1 leaked towards the outer part, but I suspect number 6 did it inside of the intake port. This flooded the cylinder killing cylinder 6. Lesson learned, always buy OEM fuel parts. Note the difference. OEM left, Buna right; Now the dyno results. The car runs much better with the stock manifold. You can really feel that the tune is correct for this type. Despite running quite smooth throughout the rpm's, during the first run the engine went extremely rich again at just 242 rwhp, note how the AFR falls of the scale like it did with the manifold as seen in this topic. So I pulled and plugged the vacuum hose again and the power rose to 255hp just 3hp over my custom manifold, and 8hp less than the ITB setup. As can be seen in the dynosheet, both the ITB (blue line) and custom manifold (red line) take the lead from a low speed on. At 135km/h the AFR went very rich on the custom manifold and the stocker (green) takes over shortly, staying close till the last top end where the AFR screws up again on the custom manifold. The ITB setup is by far the best over the entire rev range, take into account that that setup wasn't done with a pulled vacuum hose so likely too rich as well (the AFR recording was faulty during the run so no comparison, but note the power drop at the end just like the very rich custom manifold). The overall design still makes it a winner. It all sums up pretty well. The custom manifold from this topic couldn't perform well as the ecu made it run way to rich, I guess a boost leak or dirty MAF as the cause. This killed the performance of it, and I feel it should be right on par with the ITB manifold. The stock manifold has the primary advantage of being tuned for the setup, giving it a false start. Add to that the effect of the stock turbo's, which were designed to work with the standard manifold's performance areas throughout the rev range. I also expect both the ITB manifold and this custom manifold to respond much better to uprated cams. At a stock stage a custom manifolds seems pointless for the marginal power gain, the money could better be spend on other parts. But at a higher state of tune, where all other 'breathing' parts have been uprated the stock manifold becomes one of the next steps. Now it's time to test one on a tuned 300zx.
I suppose this is a given really. I cant say i expected a huge outperformance when so many dollars went into designing the stock one. I would be interested to see a dyno comparison between stock everything including tune, and stock everything+your manifold & tune to suit.
