Sydneykid

Hi, as you can see mine drops off 35 rwkw and the GTR cams lower this considerably compared to the standard cams. I have also spent a bit of time minimising the drop off with fuel and ignition mapping. This is a bit hard to do if you don't log it in the first place. You can use a normal boost gauge to measure back pressure in the exhaust. Since it measures pressure (not airlfow) the hot air doesn't travel through the tube from the exhaust up to the gauge. You will of course need a heat resistant piece of hose at the exhaust itself and for a short distance thereafter. As for back pressure versus boost, it really depends on the turbine pressure ratio and the exhaust. Following is an extract from an article written by Jay Kavanaugh, a turbosystems engineer at Garret. It made sense to me of what is a complex subject or aerodynamics that always makes my brain ache; "Say you have a turbo operating at a turbine pressure ratio (aka expansion ratio) of 1.8:1. You have a small turboback exhaust that contributes, say, 10 psig backpressure at the turbine discharge at redline. The total backpressure seen by the engine (upstream of the turbine) in this case is: (14.5 +10)*1.8 = 44.1 psia = 29.6 psig total backpressure So here, the turbine contributed 19.6 psig of backpressure to the total. Now you slap on a proper low-backpressure, big turboback exhaust. Same turbo, same boost, etc. You measure 3 psig backpressure at the turbine discharge. In this case the engine sees just 17 psig total backpressure! And the turbine's contribution to the total backpressure is reduced to 14 psig (note: this is 5.6 psig lower than its contribution in the "small turboback" case). So in the end, the engine saw a reduction in backpressure of 12.6 psig when you swapped turbobacks in this example. This reduction in backpressure is where all the engine's VE gains come from. This is why larger exhausts make such big gains on nearly all stock turbo cars-- the turbine compounds the downstream backpressure via its expansion ratio. This is also why bigger turbos make more power at a given boost level-- they improve engine VE by operating at lower turbine expansion ratios for a given boost level." Hope that helps:cheers:

What I would do; * Increase the bore to 87 mm = 2.5% increase in capacity to ~2,630 cc's * I would also increase the static compression ratio at the same time, get it up to 9 to 1. * I would go for 264 degree cams with about 9.7 mm lift (I prefer Jun for their lift/timing combinations) * The increased camshaft overlap will lower the effective (dynamic) compression ratio. * Port the cylinder head and match the combustion chamber volume (make sure to keep the standard squish). * Stick a set of forged rods in it with ARP rod bolts and up the revs to 9,250 rpm * ARP main studs and head studs of course * Give GCG a call and talk through a pair of GT25 based turbos that will make say 725 bhp at 1.3 -1.5 bar. But that's just me:cheers:

:wassup: Shoot :wassup: I think I better open up a dyno shop in Tas, that's almost double what it costs in Sydney.

:wassup: BS :wassup: Jap cars are right hand drive same as ours. Gutters are on the left, not in the middle of the road. The road cambers to the left so that the water runs into the gutters. Maybe its because they are in the northern hemisphere and the water spins anti clockwise going down the drain. Or is it clockwise PS; find a decent suspension shop and get the caster (front only) and camber + toe checked on all 4 wheels. New tyres show up any small differences, older tyres can cover them up as they wear.

Whiteline caster bushes in mine for 2.5 years no squeeks. I used the supplied grease:cheers:

If you change the uprights to GTR...... You would also need the GTR drive shafts as the wheel bearings are different. You would then need the GTR diff as the flanges are different. Then the GTST tailshaft won't fit as GTR's have CV's not uni joints So you would need to get a tailshaft made/modified. Then the speedo would need calibrating as the diff ratios are different Personally I would buy GTST shocks, saves alot of mucking around.

My experience with standard cams has been that RB20's feel OK over 7,000 rpm. They don't go flat like an RB25, but the power drops off a lot. You may be suprised when you actually measure it.

bhp / 1.34 = kw We have had over 20 X R33 GTS's on our dyno with similar mods and your power output is pretty much the average. After the FMIC, a Power FC would be on my list, with good tuning that should get you to 200 rwkw (270 rwhp). Be carefull at 12 psi, ceramic in the cat is not far away.

Hi GTRV, am I reading your graphs right? It looks like 190 rhhp at 5,000 rpm, that seems a long way short of Jay's current 400 rhhp at the same rpm. Peak torque at 6,781 rpm on yours doesn't compare too favourably with Jays at 5,200 rpm. That's a lot to give away for an extra 50 rhhp at the top end. Hi Jay, personally I don't favour much bigger than 2530/N1/T517 size turbos on 2.6 litres. Not if you want to maintain decent response, anyway. That's why the RB30 bottom end is so attractive to us. With 3.1 litres we can run 2 full sizes larger turbos (or a big single) and have better response, higher average power and more max power. We make more power at 7,000 rpm with the 3.1 litre than the 2.6 litre makes at 8,500 rpm. With the 2.6 litres we find that we are chasing more and more rpm, which costs money and shortens life dramatically. Plus the gearing becomes unuseable when the rpm gets so high, we have to change diff ratios and that's not cheap either.

There is another question, as if it wasn't hard enough already. If you had say GTRS's you might not have the throttle response to drive the 3 hairpins and come out at 60 kph. The dulled response may cost you say 5 to 10 kph, in which case the GTRS's really then have a problem and the 2530's would easily stay in front for the whole straight. I haven't back to back tested them, it would be possible to achieve a precise answer via the data logging though. What I can say is the Jap performance shops seem to all stick with 2530/2540/T517/N1 size turbos for their time challenge RB26's. When the capacity gets up (2.7/2.8/3.0) they start to look at larger turbos, but then singles seem to rule. I think centre of gravity issues may be a factor in large twins which have to be high/forward mounted due to their size. There is also the issue of total weight, a 650 bhp twin set up weighs noticeably more than 650 bhp single set up. The low/rear mount single would be demonstrably superior in both of these areas.

More timing plus more boost (without detonation) is the big advantage. I haven't retuned a car for VP103 so I have no experience there. With TurboMax we take out as much as 10 to 15% to maximise the power. But it is very trickyto balance the detonation versus power A/F ratios. Certainly not something I would recommend is done by guessing a single reduction %, stick it on the dyno and fully map it. Otherwise you are waisting some of your money on the fuel.

You rang.... You could get an adaptor made for the GTR exhaust manifolds, the GTR dumps, engine pipes and exhaust will fit. The problem is you would need 2 X AFM's or an adaptor to run 2 X turbos with 1 X AFM. You could use a MAP based ECU instead of an AFM based ECU, but then the cost really starts to spiral for no real gain. Of course you should expect a lower level of performance (both power and response) than a GTR with the same turbos. The bottom line for me is that I can get better performance out of a single for less cost and fiddling aorund.

On an R34 GTT RB25DET Neo we have 265 rwkw out of the GCG ball bearing hi flow.

Hi Roy, this is what mine looks like at 1.25 bar rwkw-rpm 180 7,750 190 7,500 200 7,250 225 7,000 200 6,500 175 6,000 160 5,500 154 5,250 150 5,000 145 4,750 142 4,500 That's an average of 178 rwkw from 4,750 rpm to 7,750 rpm. How does that compare with yours? It isn't much more than yours at 4,500 rpm, but the cams help the top end so it doesn't top over badly at 7,250 rpm which is what happens when I have standard RB20 cams in it. There is a bit of turbo selection result here, as well as cams. I don't want to sound like I am picking on plain bearing turbos, but yours displays the same symptoms I see often. They build boost rapidly at highish rpm for their (small) size and then run out of airflow (because of this smallish size). Looking at it the other way, if you had a larger plain bearing turbo, then the boost build would be even later but you wouldn't loose as much top end. On the other hand the (larger) ball bearing turbo gives slightly better boost build, but it is still large enough to give a much better result at higher airflows (rpm). Bottom line, it has been my experience that plain bearing turbos have a narrower power band, regardless of size. Time for some cams, toughen up that top end.

Based on my experiences the R34 GTR gearbox is not a great deal better than the R32/33 gearbox as far as rpm drop on upchanges is concerned. This the R34 GTR; 8,000 rpm in 1st is 4,950 in 2nd 8,000 rpm in 2nd is 5,750 in 3rd 8,000 rpm in 3rd is 6,250 in 4th 8,000 rpm in 4th is 6,100 in 5th 8,000 rpm in 5th is 6,300 in 6th This is the R32/33; 8,000 rpm in 1st is 4,600 in 2nd 8,000 rpm in 2nd is 5,500 in 3rd 8,000 rpm in 3rd is 6,100 in 4th 8,000 rpm in 4th is 6,100 in 5th The most important gearchanges on many circuits is the 2nd to 3rd, 5,750rpm (R34) versus 5,500rpm (R32/33). Closely followed by the 3rd to 4th 6,250rpm (R34) versus 6,100rpm (R32/33). I don't think 250 rpm (2nd to 3rd) and 150 rpm (3rd to 4th) is going to enable a much larger turbo selection. The R34 is definitely superior, but it isn't going to make say 2540's a more attractive proposition than 2530's on a 2.6 litre. The GTRS's would be still unworkable. Following are the ratios we use in the 6 speed dog box; 8,000 rpm in 1st is 6,000 in 2nd 8,000 rpm in 2nd is 6,250 in 3rd 8,000 rpm in 3rd is 6,250 in 4th 8,000 rpm in 4th is 6,250 in 5th 8,000 rpm in 5th is 6,500 in 6th Plus you would need to factor in the speed of the gearchange itself (milliseconds compared to tenths). I believe that would enable say GTRS's to be used, even on a 2.6 litre. Hope that makes sense:cheers:

More information please:cheers:

Do you want higher max power or higher average power?

Hi guys, anyone thinking of doing the R34 front swap, I strongly suggest you park your Stagea next to an R34 and take a look at the differences. They are REALLY substantial. The real killer is the guards, Stagea guards are very high from the mounting point on the engine bay. If you put a GTR guard on a Stagea, the bonnet would be 25mm higher than the guard. You can't just space the guard up to meet the boonet as it would then be too short and not reach down to the sills. Next is the body line (sculptures) on the side of the Stagea, they are TOTALLY different in height and shape to a GTR. If you put a GTR guard on a Stagea, the bump trims wouldn't line up by over 40 mm. I'm with Gary1, much rather spend the money on speed, handling and brakes.

Simple stuff; If the car is a manual get a Power FC If the car is an auto get an SAFC The EManage is a piggy back, so you have all the limitations of the standard ECU. But by the time you option it up it costs more than a Power FC (FC= Full Computer), which has no such limitations. I have not found anyone who can use an EManage to control ignition on an auto, so the SAFC does the fuel adjustments just as well as the EManage but at much lower cost.

Hi guys, I will post up the Bilstein part numbers once I have fitted them and I am confident that they fit perfectly and do the job. I am not going to recommend something I haven't personally tried. When I have I will post up pictures, fitting tips and tools used. The stabilser bars I have already passed on the details of earlier in this thread. Following are the other items I have tried; Front Caster adj - Radius rod bush KCA332 Front Camber adj kit - upper control arm KCA348 Rear Camber adj kit - upper control arm KCA347 (1 kit = +/- 0.75 deg. 2 kits = +/- 1.5 deg)

My suggestions; std cam timing is not the best, advance the inlet cam about 2 degrees and retard the exhaust about 4 degrees. That usually stops the compressor surge as the engine can absorb more airflow. The std ECU is a big limiter, time for a change. Not only will that fix the surge, you will also pick up a heap of power.

I have used several GCG ball bearing hi flows and never had a problem, they make the power and obviously fit up perfectly. If you add in ALL the costs, the hi flow is very hard to beat.

I have a few suggestions; * If you have adj pulleys, where do you have the camshaft timing set? * Will it handle more ignition timing at 4,500 rpm to 5,000 rpm? * What is the dump, cat, exhaust like? If you are not running a split dump that would be a good place to start. A hi flow cat may also be worthwhile if you are still using the compliance cat. Exhauts needs to be 3.25" , you might just get away wiht 3".

As most people know I don't aim for high max power, for circuit racing average power is far more important. So my RB20's won't set any records for max power output. The best I have seen is 225 rwkw at 1.25 bar, that's with; R32 GTR intercooler Power FC with boost controller GCG ball bearing hi flow RB25 turbo GTR camshafts and adj pulleys Split dump, no cat, 3.25" exhaust RX7S5T injectors, Z32 fuel pump POD, heat shield, ambient air feed Standard internals (170,000 ks) Electric fan That combo gave me good power from 4,500 rpm to 8,000 rpm and that's what made it work well with the standard gearbox and diff ratios.

The RB26 cover fits RB20, but RB25's have the VVT actuator on the front of the inlet cam (RB20/26's don't have VVT). Note the bump in the standard RB25 pulley cover. This means you have to drill a hole in the RB20/26 cover to clear it.