Sydneykid

What you are attemtping to describe is Average Power, if you do an Average Power comparison between the 2 turbo configurations it will answer your question.

Easy, I put ZERO value on bling.

Hi Tony, I agree with pretty much everything you have said, this one needs a little comment though. We should not compare the RB26 inlet with an RB20/25 inlet. The RB26 has multiple throttle butterflies, one for each cylinder, all exactly the same distance from the inlet valve. This is NOT the same as having one single throttle body stuck on the front of a plenum, close to one cylinder and a long way from others. Nissan put multiple throttle butterflies on the RB26 at great expense, in both engineering and in the parts themselves. They did it for a reason, they have stated it a number of times, that was throttle response. If they could have "gotten away" with one throttle body at the front of the plenum, they would have saved millions over the life of the RB26. As for Toyota, the big disadvantage of the central throttle body (like on an RB20/25) is height, it makes the bonnet some 100 mm higher than it needs to be. On the previous generation engines to the 1/2JZ, Toyota had central feed plenums, but they wanted a lower bonnet line so they went for the front feed. Noting that a 2JZ is already a very tall engine, even without a central inlet feed. Take a look at a well developed, high power, drag application, inlet plenum (Veilside, Jun etc) and note how big they are. The rule is minimum twice the volume of the engine, the bigger the better. Why? Because the more volume the plenum places between the single throttle body and the inlet valves, the more it evens out the airflow to each cylinder. The resulting dulled throttle response is not an issue on a drag car. My 20 cents worth:cheers:

Hi Col-GTX, since you have obviously had it on the dyno, what were the A/F ratios like? If it is leaner than 10 to 1 at 5,500 rpm then it has a modified ECU or a piggy back. Ir only takes about 5 minutes to check the ECU, just remove the LHS kick panel and take a look. Most Tuning Shop modified ECU's have it marked on the outside case, they like to show off their brand. If not, have a look at the case retaining screws, they should have marking paint on them. If they don't or its cracked, the cover has been removed which usually means modified ECU. Another good test is the speed limiter, jack the rear up, run it up in 5th and see if it goes over180 kph. Modified ECU's seem to always have the speed limiter removed. You never know, you might be lucky and it has a Power FC in it already.

Hi Jase, the DFA costs ~$70 and I bet you could sell it for three or four times that if it doesn't do much for your engine. I assume you have a larger exhaust and maybe an airfilter, they generally make an AFM controlled ECU run a bit rich. So you will get something out of it. What I was saying was, don't expect 30 rwkw like I got from the Stagea.

Hi Jase, retarded ignition kills power and response in any engine. You need an A/F meter to tell if it's too rich or too lean. The DFA load points are relative to the AFM voltage output, the adjustment (+ or -) changes that voltage as sent to the ECU. Lower the voltage and the ECU thinks there is less airflow (than there really is) so it squirts in less fuel. This obviously leans out the A/F ratios. Increase the voltage and the ECU thinks there is more airflow (than there really is) so it squirts in more fuel. This obviously richens up the A/F ratios. I wouldn't be expecting a great power increase from optimising the A/F ratios on an N/A engine. Turbos are always tuned rich standard, and when you turn up the boost they just get richer. The manufacturers do this for engine protection and it is simply not necessary to do on an N/A engine.

I am only using the DFA because the Stagea is an auto, if it was a manual it would already have a Power FC in it. There is NO comparison, the Power FC enables me to tune everything, there are NO compromises, like the A/F ratio versus ignition timing that I have to make with an SAFC/DFA. Yep, it will cost more to tune a Power FC. The DFA took me 20-30 minutes to actually tune, plus loading and unloading time, say $100 in dyno time. The Power FC would take me 2-3 hours (I am not a good tuner), so that would be $300-$400 in dyno time. But worth every cent.

A few things to note first; The blow by goes directly into the engine via the PCV valve when the engine is not under boost. This means you get quite "raw" oily air into the combustion process, but it's not under boost so it doesn't really affect performance. But it does foul up those cold heat range plugs and gunk up the exhaust, depending on how much is actually combusted. The blow by goes indirectly into the engine via the inlet (between the AFM and the turbo) when the engine is under boost. This means you get quite oily air hittting the spinning compressor, in the intercooler piping and into the intercooler. This is the worst part for me, remember the catch can concept of slowing the airflow and bending it to get the oil out of suspension. As such, the intercooler makes a great catch can, plenty of space and lots of bending. So you end up with an intercooler coated with oil on the inside, and oil is a OK insulator. That means your intercooler no longer functions as efficiently (ie; hottter air). Then you still get some oily air into the combustion process, hotter air plus lower RON = even more chance of pre-ignition and lower power. Hope that makes sense:cheers:

I have treid the "expensive, do it all style" and guess what, they are simply "expensive", they don't do it all. The concept of a catch can is to slow the movement of the air down so that the oil has time to fall out of susppension and collect in the bottom of the can. So a bigger can is better than a smaller can due to its ability (space) to slow the air flow down. Some of the larger cans have a number of simple baffles so the airflow has to bend, this also helps the oil to fall out of suspension. Personally, I have found the cheaper catch cans filled with stainless steel wool to be totally satisfactory. The wool acts as a filter as it makes the airflow bend a lot more than the simple baffles. Spend $90 on the catch can and $5 on a pack of stainless steel wool and spend the saved $300 on something that actually makes the car go faster.

Every engine is different, but I wouldn't foresee any problem, there are plenty of RB25DET's around with ~200rwk using an SAFC.

Tyre brand and size?

You will note I did say "arguably superior". The DFA has 125 load points and each load point has 100 steps, plus you can have wide steps or narrow steps (by changing the jumper). The DFA can do a mass change, at all load points, good for upgrading injectors or an AFM, then you fine tune each load point. The accuracy and stability of the DFA looks to be 100%, which is no different to an SAFC. As for tuning, I have used both SAFC (a number of times) and DFA (once) and the tuning process was exactly the same. Use the up and down buttons to change the A/F ratios and use the left and right buttons to move to the next load point. I can't see that the DFA would be any harder for a tuner to use. It just has more load points. In execution an SAFC and a DFA are exactly the same, they change the AFM voltage to "trick" the standard ECU into going to a different point on its A/F and ignition maps. The AFM voltage is the reference point for both maps, so whether you use a DFA or an SAFC you are going to get both fuel and ignition moving load points simultaneously. It could be argued that because of its superior number of load points and very fine tuning, the DFA is able to get the best compromise load point for both fuel and igntion. But it's still a compromise. Sure you can retard the CAS to avoid pre-ignition under load and high boost, but that retards the ignition EVERYWHERE. This means you are compromising the speed of the boost buiild and response at times of low load and low or zero boost. In the end it is simply a matter of choosing which compromise you are happiest with. But it's still a compromise. Hope that answered your questions:cheers: What's next for my Stagea.............. This weekend I will be swapping the 3.25" exhaust off the R32 GTST (it's getting a 3.75" titanium one) onto the Stagea. Sometime next week I will slot the Stagea onto the 4wd dyno and see what effect the exhaust upgrade had. Maybe a little more tuning of the DFA and bit of boost tuning with the IEBC will be necessary. I am also doing the cambelt service and at the same time I will slot an Apexi adj exhaust camshaft pulley on. If it arrives from Nengun before I get it on the dyno, I will do a run at zero and then tune the exhaust cam timing for the best average power I can get. It's at 133 4wkw now, I'd like to see ~160 4wkw before I do the FMIC, turbo, split dump, hi flow cat upgrade.

A quick explanation; *Boost is a measure of resistance to airflow. *If you keep the resistance the same and increase the airflow then the boost MUST increase. *But (there is always a but) by using a larger turbo you are decreasing the resistance. The turbine (and to a lesser extent the wastegate) are in themselves a fairly noteable resistance. So by going larger (or external) you are reducing the resistance. *Hence you can have increased the airflow, decreased the resistance and held the boost at the same level. However, I don't think 20 psi versus 38 psi is a valid example, perhaps an exaggeration to make a point. A real world example, by sticking a larger exhaust on the car you have increased the power, even at the same boost. This is because you have decreased the resistance and increased the airflow. Increased airflow means more power. Hope that makes sense:cheers:

I am intending to use the DFA and IEBC for 200 4wkw via a GCG Ball Bearing Hi Flow and I see no reason why it won't work. Plus I have achieved this power figure on a number of cars using an SAFC and the DFA is arguably superior.

They state 7/6 which is 7 kg / mm (390 lbs per inch) for the front and 6 kg / mm for the rear (335 lbs per inch). As a comparison, the standard Stagea fronts are 165 lbs per inch, so that's a 137% increase in spring rate. Usually for sporty road use I would be loooking for around 30% increase. I think I'll leave it at that, you can make your own judgement from the numbers:cheers:

They quoted me $2500 so I moved on. How much was yours?

John has aready posted the "after" dyno graph. It was done on Wednesday 3rd November last year. Ambient temperatuer was 22 degrees so it was a cool day for November Boost was 12.6 psi max, dropping to 10.5 psi at 6,900 rpm. John mentioned that it had a "standard dump and engine pipe", to me that means it had a hi flow cat and a cat back exhaust. Must have been a good one to be producing increasing power over 6,200 rpm. John's post is a little confusing to me, but since he mentions "end tanks" and "USA core", I assume the car had the UAS intercooler and pipework as well. So the only thing that stands out to me is the "standard ECU", I would never be able to get a "standard ECU" R33GTST to 208 rwkw. The ECU would go rich and retard (based on the AFM voltage) long before I could get to 185 rwkw, let alone 208 rwkw.

Hi, there are a few things that concern me, that would be answered by a bit more data. Do you have an A/F ratio graph? And a Boost graph? Where is the base ignition timing set at? Checked with a timimg light? This is particularly relevant in light of the zero effect from tuning the exhaust camshaft timing, this is usually a sign of retarded ignition. And that lines up with the lumpy torque curve. When tuning the exhaust camshaft timing I personally look to hold the max power pretty much as it was, but increase the average power from 4,000 rpm to 7,000 rpm. Usual results are 10 to 15 rwkw increase in average power and around 3 to 5 rwkw in max power. That's what seems to make the car the fastest. PS; I hope you are not planning on running the standard turbo at 12 psi for long periods of time in Mackay.

And if it already had a Power FC, I would vote for a split dump and hi flow cat. Then a decent clutch to hold the power, then a set of injectors, closely followed by a fuel pump to supply them. Then a pair of Tomei Poncams, a turbo, exhaust manifold etc etc It has been my experience that all of these would give a more substantial power gain than changing a plenum. Don't get me wrong, a plenum upgrade would be on my list and the UAS one looks very nice, but it sure as hell would be a long way down my list:cheers:

Nope, the throttle butterfly on a front fed plenum is further away from #6 and #5 than standard. Again nope, it's simple mathematics the air travels though the pipework so fast is hasn't time (or sufficient contact area ) to pick up any temperature. The numbers look like this; 5,000 rpm X 2.5 litres / 2 (its a 4 stroke) X 2 (1 bar boost) = 208 litres per second.

You're kidding right. otherwise you wasted your money on the full ecu replecement. You could tune igntioin timing and he couldn't, and that the biggest single factor in improving response.

Shannons for $20,000K, garaged in Sydney, so $1300.

Same result as we get, inconclusive results. The flow bench is simply not a good test in this instance Again I applied common sense and logic and I can not see how a plenum with the inlet at one end is going to be any better, in regard to evenness of flow, compared to one that feeds the plenum in the centre. To me that is illogical. I will argue with a peak power number all day, every day, heavens it might have lost 50 rwkw everywhere else. Sorry but "208rwkw" tells me nothing about how well the plenum works. The control test here would to put the car on the dyno and tune it the best that can be achieved. Then swap the plenum and without changing ANYTHING else show that it makes more horsepower. Personally I would be looking for an average power increase, not just a peak number at one rpm point. I have done this exact test with an RB26 plenum on an RB20, dismal failure, less power in most places than standard. I have done this test with a Greddy plenum on an RB25, partial success it gained power at some rpm points but lost them at others. I have done this test with a Greddy plenum on an SR20, absolute disaster, it lost power EVERYWHERE. Hence my scepticism;

As previously posted by Abo Bob, wheel bearing wear on Skylines is most unusual. It can be confirmed by checking the sideways play in the bearing. Simply jack up the suspect wheel, grab the tyre with one hand at the front and the other at the rear and attempt to rock the tyre in and out. Do the same with one hand at the top and the other at the bottom. Compare the amounts of movement. The next test is to remove the dust cover and the split pin and see if there is any looseness in the retaining nut. Also a visual inspection of the amount and condition of the grease usually reveals any bearing wear. Hope that is of some help:cheers:

I was going to let this slide, as any contradictory post may come across as being simply argumentative, and that is certainly not my intention. But it is so totally contrary to what I have experienced, I just have to ask for some more details. I have tested the RB20/25 uneven airflow theory a couple of times, and found it to be a myth. My methodology has been to test the A/F ratios at the primary exhaust pipes, which I believe is the BEST measure of inequalities in airflow under boost. Any cylinders with higher airflow would show leanness when compared to other cylinders with lower airflow. I simply have not seen that, in fact the only cylinder that shows any leanness is #6 and (as slight as it is) that can be more likely attributed to water temp differences as it is the furthest from the water pump. Testing on the flow bench can easily be flawed as it relies on vacuum to stimulate airflow, this does not necessarily generate the same airflow patterns as when boost is introduced into the equation ie, suck versus blow. The question is then, how were the tests carried out? And how was the extrapolation to boost conditions calculated? This one is even more difficult for me to understand. If this were in fact the case, then in an RB25DET with the usual 6 X 90 degree bends, you would see a 1.5 psi difference in the boost pressure at the intercooler outlet tank compared to what you see at the throttle body. Having tested this many, many times, when selecting intercoolers, I have yet to see even 0.25 psi pressure drop. Testing this on the flow bench can easily be flawed, as once again it relies on vacuum to stimulate airflow, this does not necessarily generate the same pressure drop as when boost is introduced into the equation. So the same questions apply, how were the tests carried out? And how was the extrapolation to boost conditions calculated? I expect that John may not able to answer the questions himself, but I am sure the testers will be able to fill in the gaps.