intake manifold beginning

[thespeedfactory]

Built RB26's Rev to 9000 rpm and make max power with that plenum size.

I understand the 100%-150% plenum size but I am am trying to compensate for only one cam and making max power at 6000. I should be at about 90% with this plenum.

If it doesn't work we can put in tubes to connect all the runners about 2" from the plenum. That shoud technically increase the overall plenum volume, and alter the pulse wave.

As far as the dyno, there is not a working one on island. So a big fat no go with that.

[5mall5nail5]

Someone more well versed in fluid dynamics can speak the truth but I wouldn't think it'd matter whether it revs to 20 rpm or 9 million, if its flowing enough, the plenum may not be enough. The runners add volume but that's not usually how you calculate it. By time the air is in the runner its being accelerated pushed to the valve (or pulled), and doesn't really attribute to how much air is in the plenum because its not in the plenum.

I just think it's a little small especially if going through all of the work. You could easily grab extrusions from Ross Machine and make something way nicer with much more volume. The long runner is nice for around town but if this is going to be a boogie car I would think you'd want shorter runners. The M30 makes good torque even NA, so it won't be needing more and with such long runners it might only be available for half the rev range and horsepower might hurt on the top end. Just things to consider!

[So Live]

Jon, I think hes saying the runners are a decent amount shorter than stock so he shouldnt be hurting performance as far as the runners are concerned and he'll still have some length to keep some bottom end.

Looks like a cool project dude! Im a little weary of the plenum volume too but if it works better than stock, it works.

[SiGmA]

Hey I'm curious, what type of drag racing do you do that only races to the tenth mile?

[thespeedfactory]

HKS/Omega drags at Nago Circuit. 150M only

Sucks...but that is why my build is a bit off the norm. I am building it for 150M not the 400.

The track is not long enough to get to "top end". If I want to be competitive I need to have my numbers down low.

~900+ AWHP GTR's run 5.4 sec in the 150 and the RWD converrted ones run a bit quicker.

[SiGmA]

5.4 and 900WHP? That is dog slow!!! Donovan makes ~800WHP and laid down a 4.005 in the 330', which is 100.58M.. And they have the advantage of AWD vs RWD, which almost always helps drop launch time a lot! My run is a lot like the run in the left lane of this (I do the 8th in 8.559@91.28/quarter in 12.846@116.64) and I was putting down MAYBE 400WHP.


I look forward to seeing your project completed and running tho!

[thespeedfactory]

four words

not a prepared track

There is zero traction out there and it is crappy asphalt with coral dust mixed in.

Basically worse that a standard public road in the US.

I am spinning MT drags in third.

VHT is not allowed.

On a prepped track they would be running 9 sec 1/4 easily

The A class RWD GTRs are running 4.6's. The 5.4 was an AWD full interior steet car with no traction.

[black bnr32]

[QUOTE=thespeedfactory;17823637

As far as the dyno, there is not a working one on island. So a big fat no go with that.[/QUOTE]

Jeez... how the heck do the japs tune?

[SiGmA]

Originally Posted by thespeedfactory

four words

not a prepared track

There is zero traction out there and it is crappy asphalt with coral dust mixed in.

Basically worse that a standard public road in the US.

I am spinning MT drags in third.

VHT is not allowed.

On a prepped track they would be running 9 sec 1/4 easily

The A class RWD GTRs are running 4.6's. The 5.4 was an AWD full interior steet car with no traction.

Wow that is pretty insane man. That really has to make racing a lot less fun! Do you guys have decent road courses?

Originally Posted by black bnr32

Jeez... how the heck do the japs tune?

He lives on an 877mi² island, not the main part of Japan. Very small southern island. I'm sure they have dynos on the other bigger islands.

[YellowBed]

What island are you on?

[thespeedfactory]

Okinawa

[wheresmym3]

You a Marine? Looking forward to more progress!

[thespeedfactory]

USAF

Should have the car running by Saturday.

[YellowBed]

sail to japan and dyno it. :P

[lughed]

I think you will be good with that manifold although it might actually push the peak power out of the m30's range.

[thespeedfactory]

pics from today. Wednesday for starting it up??? Finished the wiring up today with cutoff switches for fuel and 12 switched power. Wednesday I am putting a switch in the coil power wire. This way after I install the nitrous, I will have the capability to crank the motor without any fuel or spark.

Just incase I forget to turn the bottle off and my N2O solenoid springs a leak.

[thespeedfactory]

We estimated the plenum volume to be about 3.25 liters. When the welding is done I will be taping off the TB inlet and filling with water to the runner level to verify.

To put it in perspective, the water bottle that is sitting on the ECU box in the first pic is 1.8 liters.

[DTRguy]

Originally Posted by thespeedfactory

We estimated the plenum volume to be about 3.25 liters. When the welding is done I will be taping off the TB inlet and filling with water to the runner level to verify.

To put it in perspective, the water bottle that is sitting on the ECU box in the first pic is 1.8 liters.

The Water fill test is how I test plenums' for volume. I have done it for EVERY plenum I have made. It's a great test if for no other reason that to just know. I have even cut apart a plenum and made it bigger after doing this test. If my math serves me correctly 3.25l is going to be 116% of engine volume... that isn't bad honestly IMO. Get the actual volume once it's all put together and see! You did say you had a 2.8l right?

[thespeedfactory]

3.5 liter

We will see how close to 100% I get when it is all welded up. Finalized the wiring yesterday. All the wiring is self supporting now. The only thing by OEM wiring is providing is lights and blinkers.

Took time off today for my son to ride his bike...had a little clutch problem he needed to fix.

[e34biturbo]

Originally Posted by DTRguy

The Water fill test is how I test plenums' for volume. I have done it for EVERY plenum I have made. It's a great test if for no other reason that to just know. I have even cut apart a plenum and made it bigger after doing this test. If my math serves me correctly 3.25l is going to be 116% of engine volume... that isn't bad honestly IMO. Get the actual volume once it's all put together and see! You did say you had a 2.8l right?

school me a bit here.....

sooo if you have 2.8L motor and a plenum with 3.4L capacity is that bad?
or is more volume supposed to be good.

[DTRguy]

Originally Posted by e34biturbo

school me a bit here.....

sooo if you have 2.8L motor and a plenum with 3.4L capacity is that bad?
or is more volume supposed to be good.

Well, no, not for fuller range power (read more mid range). It is all somewhat theoretical... but there is too much of a good thing when it comes to plenum volume. There are a few things to consider: length, size and design of the intercooler plumbing; size of the Intercooler; size of the turbo; design of the manifold etc. All these things combined create a power delivery type. Looking at one of these in and of themselves doesn't give a complete picture. But with respect to manifold volume the theory is that 100% and smaller will provide a peakier power band. Exactly why I can not exactly tell you. Closer to 125% and you get more midrange and driveability characteristics. Too much volume and you can get lag due to volume that needs to be filled prior to boost onset. It would seem to me that too little and the engine doesn't have enough volume in the plenum to serve itself air during the middle RPMs while accellerating. Your plenum is at about 121-122% Which is honestly very good. Nothing wrong with that IMO. My information is honestly born out of R&D from building quite a few full turbo systems and seeing if what I was shooting for was achieved. So far, every time I have set out to create a style of power band I have achieved it. With my car I wanted VERY SMOOTH power delivery with an abundance of power everywhere that I would have to electronically control through boost etc. I actually found out that even at my lowest boost setting I have more power than we need! So, again, it would seem that I have acheived my goals. I hope this helps.

And to OP, 3.5l engine with a 3.25 plenum... hmmm Driveability might suffer, but then again, it is in the end a 3.5l engine! The combination although not optimum for full range power may serve you quite well based on what you are attempting to achieve! Proof is in the drive though!

[5mall5nail5]

Its funny though because people always say "the volume needs to be filled". Are we forgetting we live on earth? There's air everywhere. In fact, everywhere on land there's pressure too. So, there is no "volume needs to be filled" because the intake plenum is not being sucked dry of air. Its a silly thing people constantly state and it really makes no sense. Think of air as water. Is there ever a time you would pour water into a cup and it would take time to fill up because there's a void of nothing there?

[DTRguy]

Originally Posted by 5mall5nail5

Its funny though because people always say "the volume needs to be filled". Are we forgetting we live on earth? There's air everywhere. In fact, everywhere on land there's pressure too. So, there is no "volume needs to be filled" because the intake plenum is not being sucked dry of air. Its a silly thing people constantly state and it really makes no sense. Think of air as water. Is there ever a time you would pour water into a cup and it would take time to fill up because there's a void of nothing there?

maybe I misspoke... but air is not water in the sense that water doesn't compress... so volume as in the case of a manifold or say even a tire has a difference in filling. 32psi in a car tire vs. 32 psi in a bicycle tire... which has more volume? Which takes longer to reach that pressure with the same filling source. THAT is what I am saying. The time in which it takes to reach the predetermined pressure... hence filling.

[e34m535t]

Nice work! I cant wait to see how it performs.

My understanding is the only real downside to a large plenum with single throttle body is throttle response. So for Drag racing an oversized plenum might not be a big issue. Ive been working on a manifold for my m30, and the plenum is in the 1.5-2x engine displacement range.

[5mall5nail5]

Originally Posted by DTRguy

maybe I misspoke... but air is not water in the sense that water doesn't compress... so volume as in the case of a manifold or say even a tire has a difference in filling. 32psi in a car tire vs. 32 psi in a bicycle tire... which has more volume? Which takes longer to reach that pressure with the same filling source. THAT is what I am saying. The time in which it takes to reach the predetermined pressure... hence filling.

Pound per square inch. Pressure != volume. Honestly 0 psi in the intake track would be best if using a turbo because then somehow ALL of the air thats being displaced by the turbo is being consumed by the engine. Its a volume thing, not a pressure thing, and there's never "no air" in an intake, so "filling" isn't really what it's all about.