Sidwysracr

Yeah, $279 for the base of the kit seems pretty good. But you have to buy the supporting sensors, ie.. pyrometer is $89, 3.5 bar MAP sensor $115...

Beerbaron nailed it on the spot. XD-16 are now MTX series. Very interesting indeed.

Here are results from a wideband shootout, you can google and read how they compared it along with a industry sniffer. Innovative is both accurate and quick to display it's numbers.

Just curious, does John have a dyno with the comparsion of the -5's and -10's?

I will also be interested in dyno graphs. Do you have graphs of the -5's and the -10's? And please post the dyno of the efr pair. Much appreciated.

Geoff, From reading around maximum is 2.5:1 ex/in pressure ratio. I have checked with the matchbot for both the 6255 and 6258, both exceed your 1:1, ratio. They are 1.6:1 and 1.5:1 pressure ratios, respectively. From talking to several tuners. This is optinum. Ultimately I been trying to compare them to the GT2860r-5's, and if they fare well I will purchase a pair of EFRs. I could use help by a dyno chart of either 6255 or 6258, and the boost graph included. This would help my decision matrix. Thanks, Joe

I do not plan to keep the A/C, since I am building a track car. I am trying to pursuit response, with 500 to 600 mid to high rpm power. I see on the website recommends the 58 as well. As before mentioned goal, knowing that the smaller turbine will spin quicker at cost of higher back pressure and more waste-gated at max boost. What would be the benefit of the 58 over 55? From just looking at the compressor charts alone, I can meter about 400 rpm for the 6255/6258 62 mm compressor wheel can achieve maximum boost sooner than the GT2860R-5's. And as far as fitment issues, is it possible to use stock fitment for a pair? I am seeking low-mounted as I am trying to keep the center of gravity as low as possible; it's a track car. I know that the dump-pipes will need to be V-band, if I can get away with stock manifold fitment then it can effectively reduce my costs by saving me the design/custom work and it allows quicker replacement as well.

Hello Geoff, I noticed that there are 7 turbos, but you only sell 6. I would assume you buy the 6258 and request the 55 turbine wheel? http://www.full-race...efr-turbos.html Also, does these have better boost climb than the GT2680R-5? I am seeking a twin low mount set. And with the single scroll 0.64, if I am reving up high what BP ratio should I be getting if I am rolling with 18 to 22 psi? From what I know the GT2680R-5 can hold it's power to 9k rpm with ar 0.64, so I would expect same with the EFRs. And finally, any recommendations of set up, such as sticking with 58 wheel, etc etc. Thanks.

Bump for nismoid

crazy? maybe 11:1...or even 12:1 with E85... many can do all day with those comp ratios.

To be honest. I am looking at a 500 to 600 range of power. I will be hooking up on rw only. The engine goodies will be replaced forged internals (2lbs of reciprocating weight reduced), I am going to do minor head work. Possibly spring and valve replacement to support higher revs. I am looking at tomei 260in 10.25 lift and 252ex 9.15 lifts. 9.5:1 to 10:1 seems to be a magic number, considering that good number of turbo cars are coming out 9:1 from factory. I can reason this is due to better electronic modulation. And I would assume a AEM ECU unit would be a fair bit better than current stock ecu's to modulate the engine. As I mentioned before I'll be running a 4.363 final drive over my recent 4.1's. this is roughly 400 to 500 rpm per speed. I believe this will reduce the variance between the turbos. And I am running a 6-speed which the ratios are : 3.794 2.324 1.624 1.271 1 0.794 which calculating the end of all of the gears at a 9000 rev limit, is 40.1 MPH, 65.5 MPH, 93.8 MPH, 119.8 MPH, 152.3 MPH and 191.8 MPH, respectively. I honestly believe that there shouldn't be a drop of 3000 rpm per shift. Which put you somewhere above 6000 rpm. This is my dilemma in thought, even if I make 500 hp with -9's it won't have the poof before 9000 rpm; this would effectively reduce my boosting time and time in gear. Including that I am not likely to fall under 4000 rpm as well. The -5 have an efficiency island of 77% and the -9's are 75%. Comparing the range that engine will be running though from the compressor charts the -5's will be running cooler. With those parameters, how much response difference would there be with the -9's and -5's even if I opt to push only 500 hp? How long can I stay in gear if I choose the -9's how about the -5's? I am sure to recon that the one that stay's in gear at a longer rpm range will be quicker, especially when your rpms are climbing like hellfire due to the larger final drive. And btw, I am looking at 2500 to 2800 lb vehicle.

Bump

First... whatever mindset/chip in your shoulder about the heated -5/-9 debate... leave it in that debate thread. I never said they were equal, where ever you get that from. I already stated reasons why the -5 are good to have still on the table and it has potential to deliver more power if needed. Finally, This thread is about running higher compression with boost, I am seeking knowledge from ones who have done it.

I read a lot about -9's and -5's. -9's fit a perfect to street car for what most people say, but once it reaches the upper rpms it runs out of it's puff, this is where the -5's shine. Here's a dyno graph with a comparison of -9 and -5's, the taller line is obviously -5s, but you can see that the -9's match the description as above.. and notice that the -5's are only 300 rpms behind. But notice the torque curve... even though not sooner, but it allows you to say in gear longer before it dives down. They follow nearly nearly identical paths on the up climb (the difference noted above), the -5's does it more efficiently. I plotted both the -9's and -5's compressor maps. Like I said 77% over 74%, less hot air the better. Tuning and cams can make the -5 spin sooner. I am after a track build, what ever gets me around the corners faster and have enough top end to keep up in the straights. Raising CR will allow more off-boost power, which for a tracker that means a fatter power band to be used. My differential ratio is 4.363, so naturally in the higher rpms...with this...it would make the -5 spin sooner...and in the end I would have a lot of top end too. A bit of tuning can make the -5's respond sooner as well.

Yes.. -9 and -5 are both on table. No VTC is not an option. From reading one with 11 to 12:1 can run E85 all day boosted. But I am more concern with pump fuel because it's more common.

^ I been thinking about it a lot actually. I been stuck. The reason why -5 stays in the fight... is because it has more top end. And at 500 hp it is more efficient, 77% whereas the -9's at maximum is 74%. This means the the air is less hot when it's exit's the turbo. Or ultimately a cooler air charge. And for a higher compression motor every little bit helps. And from reading around the difference of 500 rpm of response can be made up else where. That's why it's still a card on the table. Other news: Also reading up... 70 cc is wrong for the volume of the chamber..it's more close to 63cc.. and if the deck clearance is 0.5 above... then my calculation says that only 0.7 mm needs to be shaven to get a 10:1 ratio But ultimately I need to know if anyone who has experience with this CR. How much of the upper rpms can be played with since ignition timing is shortened. And using if any effects using a 260 cam duration with 10.25 lifts. Thanks.

I been thinking about running higher compression ratio. Note this isn't a debate thread. I would like to get up to 10:1 CR (I can settle with less down to 9:1 min) and eventually roll with gt2860-5s.. maybe -9s.. making around 500 hp, goal is to make a super responsive machine. What I have is stock rb26 block and heads. I already have 86.5 pistons w/ 16 cc dome volume, manufacture states a 8.5 CR for these pistons. I used a quick compression ratio calculator, assuming the rb26 heads are 70 cc. I calculated with a 1 mm HG that 2mm would be shaven off. However, with no idea about piston deck clearance height that 2 mm may be more or less. The ultimate problem rests on the valve clearance.. and if I were to do a 10.25 lift, how much would I have left =/ Anyone have experience with increasing CR in a rb26 and boosting decent power?