Hey guys,
New to the forum, but I've been lurking for a while. I've been a bit lucky recently and got handed an opportunity to get a rather large discount on a turbo kit (T25 flange)
Question is however, what turbo should I go for? I've had a few on my mind and I don't mind paying a bit of a premium if it saves my ass in the long run. I've currently got the following turbos shortlisted. 280whp is probably the most I'd ever want out of the turbo once I build my block, preferably 200 whp before I start modifying the internals.
BorgWarner EFR 6258/6758 - I personally opted for a 6258 initially, but the kit manufacturer said that the 6758 is a far better turbo. My worries with the 6758 is that it might blow up my block down the road. I like these for their supposed fast spooling. (Drove a NB 1.8 with a TD04 and that was lots of fun, but it did lack a bit of power)
Garrett GT2554R and Garrett GT2560R - Tried and true on MX5's, but I heard the 2560 doesn't spool as fast as a 6258 and the 2554R isn't quite up to the task of 280whp once I go built
Garrett GBC20-300 - Suggested as an alternative by the kit supplier, but journal bearing is off-putting. Worried about how these spool. Can't really find much about them online either
Pulsar G25-550 - Knockoff Garrett, not sure if I'd want this.
What are your thoughts? Anything I'm overseeing? The 6258 is the one I'm still leaning the most towards to as I'm afraid a 6758 will straight up murder my block even at tame settings. Pump gas here is 98 octane (93 US) - Magic corn juice (E85) doesn't exist here unfortunately
EFR has a different flange than a T25, and a 2560 is going to struggle past 250whp, from my understanding. The difference in spooling between a journal and ball bearing is a few hundred rpm typically so I wouldn't fret over that, personally. Buying one part to fit another because you get a good deal can prove frustrating at times as you may end up compromising on aspects you may not want to.
The 2554 will spool fast, but I believe 250 whp is all your going to get out of it. My friend got over 300 whp on a 2860. It would spin rather wide, sticky tires at mid range, just by stomping the go pedal. I don't know about the others. If you are building a forged motor capable of running 280 whp, you should get the best turbo for that application. You can always run low boost and timing in your stock block, to keep the oily parts inside of the block.
My car only has 220 whp. You have to be very careful in the morning, if there's dew on the road. Getting sideways at 65 mph will wake you up quickly. I won't even drive in the rain, unless I'm stuck somewhere. It's very easy to spin in the rain. It would be fun, but IMHI over 250 whp is starting to get impractical as a daily driver. I would turbo my stock block and learn how to handle that power, like you're going to. You may find 280 too much, at first. You can always tyrn ut up. The supporting mods go up exponentially when you go over 250 whp. Cooling becomes much more difficult. 5 speed trans break. Definitely need stronger clutch. Good luck on your build and keep posting.
Thanks for the insight. I can choose between the EFR and the Garrett turbos. I thought they were interchangable since they both fit on a T25 flange (Or atleast, that's what the internet leads me to believe if I look around....)
I've got a 6 speed and a 3.6 Torsen diff, so I know I'm safe in that regard. My biggest concern are the rods and pistons, which I plan to tackle after this.
On a sidenote, While I've got the thread up here, I suppose I might as well ask another question. Originally before I got this opportunity thrown in my face, I was thinking of supercharging the NB. I still want to keep the driving dynamics of an MX-5 with a snappy throttle response and a linear power delivery. With that in mind, which turbo would be the best based on the choices above?
My mistake, there are t25 flange EFRs. Typically a smaller turbo is going to give you "snappy throttle response" which is one reason why many oem manufacturers use smaller turbos. A 2554R would definitely do that but won't meet your target of 280whp. A EFR is definitely the best all around choice.
I went with an EFR6258, following similar reasoning to yours. Still on the stock block right now at about 220whp, one day I'll build the engine and go for 300. I've heard of the GT-2560 getting up to the 290s, touching 300, but it takes some aggressive tunning, probably not the turbo to run.
Another option is a GTX-2860 Gen II, or the Pulsar clone, it should perform pretty close to the EFR-6258, maybe slightly slower spool, and maybe a little more top end power.
With either turbo, you will want to run a low boost wastegate spring and use boost control to keep the power in a safe place on the stock engine. I recommend the TurboSmart IWG-75 over the manufacture low boost cans because they allow customization. The IWG-75 comes with a variety of springs allowing you to dial in the minimum boost threshold quite well. The IWG-75 is especially handy for the EFR as the current IWG-75 has a ball-joint in the actuator arm that prevents binding. Binding is an issue with the EFR if you aren't absolutely spot on with your turbo clocking, and will lead to overboost. All-in-all it's worth the additional cost.
To replicate your desired supercharger power delivery, you want to raise boost with RPM using electronic boost control. A fast reacting turbo with a wide boost range is what you'll want, either turbo should be capable if you use a low boost spring, maybe you'll want a 4-port solenoid when you shoot for 300.
Cheers, that's absolutely what I was looking for. You reckon the 6258 will be a better choice than the 6758? I don't think I'd need the top end of the 6758, but the kit builder says it's leagues better than the 6258 (And it's 50 eur cheaper, but that's not important.)
Also, since I've got no experience with this, how hard would it be to get the IWG installed on the turbo? Is this something the kit builder could do without much hassle?
pretty interesting, anyone have any tips for a VVT in an NA chassis? specifically adding a turbo