djessence

Are there any threads that definitively show what impact the various options for the 6 port engines are?

From what I can tell there are opinions on:
-Leave it stock "the engineers" etc (emissions, driveability etc)
-Wire them open (and remove air pump?)
-Hook them up to exhaust actuation (RB presilencer - with air pump removed)
-Remove them completely and somehow block them to not have intake leak.

There seems to be a lot of opionin back and forth with no real information on the impact of the variety of options.

I'm trying to figure out the best option to run on a 6 port swap into a first gen endurance racer. Where can I find this? The archive threads are more of a conversation of I could/I did and I have no idea..

Thanks in advance
Jesse

Akaviri

iTrader: (1)

Yes it's worth it to have the actuators set up properly.
- No actuators is a loss of power where you'll need it the most, at higher RPMs.
- Wiring them open is an easy hack job, but you kill your low/mid range horsepower.
- You can use exhaust activation, but depending on your setup it may not come on at an ideal RPM.
- You can set it up like the S5 using your air pump and an RPM switch. They will come on at the ideal RPM every time.
- You can remove/block them, and use a 4-port setup. This requires tuning and I'm not too familiar with it.

If you're building this engine from scratch for racing, it'd be worth researching 4-port NA builds to see if it's something you're willing to undertake. There have been some great results.

Otherwise, I'd recommend RPM switch and air pump activation. It's accurate and reliable. There's a reason they got rid of exhaust activation on the S5. It kinda sucks.

clokker

iTrader: (2)

You might consider adding carbs/ITBs to your option list.

Both delete the stock manifolds altogether and thus, bypass your questions.
The carb would be dead simple, which could be a real boon to an endurance machine.
ITBs would be more efficient but the injectors would require an ECU, adding complexity and failure points.

If it matters, I'll add that the complete stock S5 intake manifold weighs @35lbs, all sitting above the engine.

lastphaseofthis

iTrader: (8)

if you're racing i would just leave them out, you shouldnt be below 5k anyways..
street cars get electric lumbar pump, tank, check valve, and rpm switch.

RotaryEvolution

iTrader: (30)

if it's allowable this is very true, a carb would be best for high end power over the limited variable intake system on the street cars.

but carbs aren't always all that simple, dead spots and flooding in high Gs as well as fine tuning the jetting isn't for everyone.

clokker

iTrader: (2)

I agree, but then again, not everyone endurance races and tradeoffs are part of the deal.
IMO, the number one priority of an endurance racer is finishing and absent a Porsche/Audi budget, in amateur ranks that's most easily achieved through simplification.

A lifetime of SU/Weber experience tells me that yes, carbs are a pain to setup but they rarely fail totally and the engine will run even in that less than ideal condition. Introduce injection/ECU and performance may well increase but so have the number of potential failure points.

Also of importance is considering the tracks the car will race on.
Unless you're at Road Atlanta or Laguna Seca, most smaller tracks have no place to really exploit top end, outright speed is not the main priority. A carb would be perfectly suitable for someplace like Roebling Road.

Besides, endurance racing WILL expose weakness you never even thought of in car and you'll be busy dealing with either mechanical issues or accident damage, so it makes sense to anticipate/eliminate as much as possible beforehand, certain in the knowledge that something is gonna get you.

Just ask Toyota about LeMans.

j9fd3s

iTrader: (3)

for racing take them out. remove the shafts, and just plug the holes with something. the 6 ports open at ~3200rpm, and when you're racing that means they will always be open anyways.

also without that whole system, its one less thing to worry about.

100% correct. we've done four 25 hour races, and just getting a car to run that long is not easy. we start with a fresh car too (new engine/trans/diff/shocks/bearings/bushing/etc). i'll keep it short, but 3/4 races we have finished without the hood.

b) we're like 1/2 second off the in class lap record at laguna seca (PTE/TTE) and our fastest speed is only like 92mph, right before turn 5. way different than autoclub speedway, where you are over 120mph on the banking (behind a 792P, was pretty awesome)

historically the rotary is bulletproof and will happily run all day, its the rest of the car. you will learn, with a 1st gen, to just bring an extra pair of struts, and just change the whole strut assembly halfway through. bring an extra rear axle, fuel pump, transmission, etc etc

djessence

Thanks for the various tips and advice everyone. We did consider going to carbs but I'm not sure we have enough room on "modification points" left after the engine swap to then go to non stock (on that engine) induction.

We have run the carb'd 12A for 3 years in this series now and have been nothing but impressed, have sorted out all (at our current speed) issues and weakpoints with the car and now the inevitable speed creep has occurred in the series and we are finding ourselves being left behind on the straights now.

The sparing is very true. We besically carry an entire drive train. We have each front corner, full change of brakes, complete rear diff/axle assembly, driveshaft, engine and transmission and basically a full fuel system. In the first year we basically needed all of it and for the most part have sorted out our cooling issues, shifting and braking concerns and now in the past 2 years, we have only needed the rear axles so far due to some bearing issues (which we have now sorted through set run life on them).

I'm sure with 40 more HP, we will now find new limits on various components.

djessence

A bit old but going through the breaking in process - we removed the ports (maybe not the best option, not sure) and we find that at low RPM, high load (say 20km/h and WOT) we see AFRs skyrocket - is this something the stock ECU should be able to compensate for or is this something we would expect given the ports removed? Its soemthing we noticed during testing but have limited space to do a full pull. Didn't notice the AFRs in 1st and 2nd but in third doing pulls, the AFRs shoot way up.

j9fd3s

iTrader: (3)

way up, like high number? like lean? i don't really recall, but if you had a completely stock FC, in say 3rd, and just went WOT at idle, its pretty lean until ~4000rpm. AFR is in the mid 14's, and then around 4k it starts heading richer. the S4 goes to mid 12's, and stays there, the S5 hits mid 12's and then goes to about 10 by redline. the S5 had a 7year 70,000 mile warranty on the cats...

the lean mixture under 4k is all for emissions, its lean enough that the cat works, and then they just run really conservative timing to keep NOX and detonation away. over a certain point, they stopped testing emissions, and the cat gets too hot, so then the S4 is just tuned normally, and the S5 is tuned for the cat warranty

Edit: and come to think of it, but i had an S5 vert, and it started completely stock, and then i added a cat back, then an intake, and it was fine, made power, good noise, etc. then i pulled the cats, and it would do this thing in the 2500-3500 area where i could go WOT and it would make noise, but not really go anywhere. i didn't check it, so i'm not really sure what the deal was, but i'm pretty sure it was too lean. for sure the tune was too far off in some way. i put the cats back on.

BTW i put an EGT in that one, in place of the o2, and EGT would only hit about 700c, and beating the crap out of it, it peaked at 710c