So I decided to look at the graphs a bit more and decided to look specifically at 15psi. All 3 turbos have all points well within the surge line at 3,000RPM and decided to look at what RPM range do the turbos have an efficiency of at least 70%

6258- 3,700-7,500RPM
6758- 4,700-7,500RPM
7163- 5,400-7,500RPM

I also decided to look what efficiency island each turbo was at, at 3,500RPM at 15PSI.
6258- 68%
6758- 61%
7163- 60%

So from this information, is it reasonable to say, all 3 can make 15PSI at 3,500RPM, but due to less efficiency, the air will be hotter for the 6758 and 7163, so at that PSI and revs, the 6258 will make more power. Also, as the 6258 is at or above 70% efficiency for at least 1,000RPM more, can you conclude it will have a wider powerband?

Also, I know for me, as I am looking for more mid range rather than top end, the 6258 is probably best for me. But I just want to use the compressor map say definitely, ok this is best, rather than just relying on the basic principle of smaller turbo means less lag down low. Or I may find out the different won't be that much so better off going for a 7163.

Well with the EFR series turbos, you get the twin scroll with ceramic ball bearings I am nearly there!!


What do you mean by high boost. Is your idea of high 15PSI or 25PSI? When I originally was looking at the full race kit, max I was looking at was 13PSI with the 7163 as you could get about 350-370whp. and with that turbo, quite a few were hitting 13PSI by 3,500RPM. But then I thought to myself do I really need a turbo that big; hence why I began to look at compressor maps.


I am sure the 6258 would be able to get my aim of the 350whp ball park. the turbo is rated for 450 (pretty sure that is at the flywheel so after 15% loss, about 380whp). So I guess that means I would be pushing a lot of boost; well over 20PSI.


With the 7163 at 13PSI, I know what I would need to do; 10:1 CP Carillo Pistons, CP rods, GSC valves, DW65C fuel pump, 700CC Deatschwerks injectors, ACT XT street clutch with lightweight flywheel. By going with the 6258, the majority stays the same, but I am guessing I may need to go to 9:1 pistons?? My main concern with the 6258 is I don't want significant torque drop off. I am yet to see anyone go for the 6258. Most run the 6758 or 7163.

Also, another reason for not going for massive boost on the 6258, is I just calculated the CFM, compressor flow and pressure ratio, and at 22 PSI, the flow will be 41.72lb/min at a pressure ratio of 2.496 @7,500RPM; on the map, this puts it at 56% efficiency. Seems like the sweet spot for the turbo is 15PSI

Size is relative so fair question. Most SC and turbo kits start at about half bar (7-8 psi) on a system that has an upgraded, medium-sized turbo over most oem turbos. Seems like oem like to use smaller turbos with higher boost levels like 1-1.5 bar or 14-21psi. This is probably to avoid lag, and they don't boost higher because higher boost levels could be either unattainable with a small turbo or dangerous without e85 as a knock suppressant or unreliable because of excess heat from inefficiency. Before e85, on the street, 20+psi was high boost. Now guys are running 50psi, but to me, on pump gas, 20psi is high.



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I'll let you know how this goes (ETA 1-2 Months):

Borg Warner EFR6258

Power aim:360Whp (265kW)

http://i256.photobucket.com/albums/h...356/export.jpg

You legend!! What kit are you using? Do you have a build thread that I can follow?

hahahaha No build thread unfortunately as yet but its definitely something that'll happen before the install.

Its a Sydney Motorsport Engineering EFR kit which looks something like this

http://i256.photobucket.com/albums/h...96176186_o.jpg

I have the turbosmart wastegate and blow off valve, ceramic coated hot parts + full dei titanium heat wrap

Clutch and fuel pump to go then full flex tune.

I am surprised there isnt much info on the borgies for this car. I'll fix that with heaps of pictures and videos!

Very interesting!! I am also from Sydney. Will definitely be looking at your build.


I am also surprised the little attention Borg Warner is getting. Out of the little information available, all relate to the bigger 6758 and 7163.


With your 260wkw goal, do you plan to achieve that on 98 or E85?

There are a few others here who have Borg Warner

I've been full time Eflex (E70-E85) since 2.5 years ago or so.

I believe 300hp (212KW) is about the limit of 98 (or 93 for US), I have have a hate relationship with 98 RON due to the significant IAM drops it produces. Australia's fuel is so bad unfortunately.

So yeah going to request ultra safe 98 tune (coudnt care less if it produces 20kw) and 260kw on e85

Sorry if this is a thread jacking, I promise i'll post info when it comes :)

Sorry I meant the 6258 specifically. There are a few very good threads relating to the 6758 (treadstone) and the 7163 (full race thread).

I am assuming then you plan on doing this on a stock motor. Also definitely not thread jacking; I am happy I will be able to refer to someone using the same turbo.

yeah stock motor, Tyler at PVS is the desired tuner and he ran the same kit 260wkw on the track for a long time without any issue at all. I believe hes now running it at 313 or 330kw tracked still going strong

Knock down a super solid tune, dont go too high on power and respect the car and you should be alright IMO

I was actually a little worried the 6258 might be small for the intent but the discussions here really brought up my confidence

So excited!