SVreX MegaDork
3/25/17 9:28 a.m.

Some of you speak turbo very well. I do not. I couldn't tell you the difference between a T28 and a loaf of bread. So go ahead and treat me like a 5 year old.

I thinking of upgrading the Mumpkin. It currently has a cobbled together T25 (I think).

I am looking for better than 250hp. I realize 300hp will probably mean rebuilt internals, which I'd like to avoid. But I am prepared to do the best I can on the turbo side, and risk the engine.

The car currently has a 1.6L, and we've boosted it to the moon. But I am pretty sure we are just making heat at that level- no power. We posted nearly identical timeslips to A&M's turbo Miata in 2015, but they did it at 116 mph (IIRC), and we did it at 98 mph. We had better suspension and tires for the launches, but they killed us on power.

I'd like to get the turbo setup right (manifold, intercooler, exhaust, blow-off), and the engine management, and switch to E85. But I also have a 1.8L sitting on the shop floor and would consider switching now (but I am not excited about the amount of downtime that would create).

I will definitely be working in Ebay price range.

Thoughts? I'm guessing my best option would be a T3/T4, but I am not even sure what that means. Teach me.

DeadSkunk UberDork
3/25/17 9:36 a.m.

I'll make some popcorn. A turbo Miata drive train in my Corolla would be interesting. This could be a good learning experience.

calteg Dork
3/25/17 9:52 a.m.

The "T" designation was implemented by Garret to tell you the flange style and approximate flow rate of the turbo. A T3/T4 is a hybrid of two different turbines and housing, the smaller T3 on the hot side to help with spool, and the larger T4 on the cold side to deliver more boost. A T3/T4 is probably overkill for your goals, they're typically sized to deliver 300-450hp. It also isn't very well matched for a 1.6L motor.

Bear in mind that the T25 is a ball bearing turbo, so it will flow more air for it's size than a T3 will. Absolutely use the 1.8L, you already have it, so it's free displacement. I'd also add that the stock 5 speeds are on borrowed time north of 250hp.

For your budget and power goals, I'd be looking at a Chinese knockoff of the T3 super 60, mated up to the 1.8L. Consider that for what you want ("300hp on E85, on an ebay budget"), almost nothing that you have will currently work. You'll need that 1.8L with upgraded internals, an NB six speed, new ecu, new clutch, completely new fuel system to handle ethanol, wider tires, etc. Given how cheap NB's are now, it might be a better use of resources to find a rough 6 speed car to start with.

SVreX MegaDork
3/25/17 10:03 a.m.

In reply to calteg:

Understood. A car built entirely out of Ebay parts running twice it's factory output is on borrowed time no matter what you do to it.

Are you saying the T25 is a better choice for this engine? How about the 1.8L?

So, a T3, a T4, and a T3/T4 all use the same flange?

SVreX MegaDork
3/25/17 10:06 a.m.

In reply to calteg:

What's a Super 60?

NordicSaab HalfDork
3/25/17 10:26 a.m.

A T2 turbo can easily do 300hp+... I dont know what your price range is but a t28 sounds like the easiest solution here.

T3 will be cheaper, take more time to install, and have a phenominal amount of lag(compared to a t25).

SVreX MegaDork
3/25/17 10:30 a.m.

In reply to calteg:

I agree about the NB car, but you missed one part of my goal. "300hp on E85, on an Ebay budget, and SIMPLE".

I've got a car that is perfectly capable of winning the autocross. I've also got a car that is capable of reasonable launches (1.9 second 60'). I was beaten by a similar car that simply had more power, seat time, and tuning time. The seat time and the tuning time is free. I need to bump the power.

So, my choice is to try to squeak more power out of what I've got, or build a new car from scratch. I'm leaning toward bumping what I've got. I don't have time to build an entire car before Oct.

Keith Tanner
Keith Tanner MegaDork
3/25/17 10:35 a.m.

If you go with the 1.8, you'll get 10% more power for your efforts.

T28, etc, isn't current terminology but it gets you an idea of the size. Garrett fixed all their model names a few years back but the junkyard turbo community isn't quick to change. A T2, T25 and T28 all use a T2 flange. T3, T3/T4 - those use bigger T3 flanges. A T4 uses a... I'll bet you can guess. A T3 Super 60 is a particular junkyard turbo that I think was used on Dodge 2.2. It also has a cool name.

We use a T28 (again, old, dated terminology, it's really a GT2560R) for our standard turbo on the FM II. It's good for 250-260 rwhp on a 1.8, depending on the ECU. It's a good match to the strength of stock internals.

If you're going to go from a T25 to a T3, you're going to need either a new or a modified manifold. If you're going to modify the manifold, do the engine swap It's not really very difficult, some shop has the info online.

You can dive deep into this rabbit hole and start obsessing about turbo maps, or you can just find a turbo of about the right size and spend more time concentrating on getting it tuned correctly. For a Challenge car, the latter would be my suggestion.

Ball bearing turbos can spool a bit faster, but they don't make any more power.

Keith Tanner
Keith Tanner MegaDork
3/25/17 10:37 a.m.

BTW, we've gone north of 400 wheel hp on a T2 flange turbo Had another on the dyno yesterday with a GT3071R running a T2 flange, 296 or so on 91 octane pump gas.

SVreX MegaDork
3/25/17 10:48 a.m.

In reply to Keith Tanner:

You're my idol.

SVreX MegaDork
3/25/17 10:55 a.m.
Keith Tanner wrote: You can dive deep into this rabbit hole and start obsessing about turbo maps, or you can just find a turbo of about the right size and spend more time concentrating on getting it tuned correctly. For a Challenge car, the latter would be my suggestion.

No interest in going down the rabbit hole. Bolt on power is a better option. I'm willing to put the time into tuning.

Keith Tanner
Keith Tanner MegaDork
3/25/17 10:58 a.m.

First question, then - what's your plan for the manifold? Are you going to weld one up or buy one?

If the latter, then look to see what sort of manifolds are available at Challenge prices and that'll narrow down your turbo options. If it's the former, then you get the turbo and build the manifold to suit. If you're already running a Garrett T25, then going to another Garrett with a T2 or T3 footprint will be easiest as your downpipe will probably be pretty close to fitting.

This is assuming you're going 1.8. If you want to stick with the 1.6, you'll be giving up response to get your power levels. Drag racers will run a T3 Super 60 on a 1.6 but autocrossers might find it a bit frustrating.

codrus SuperDork
3/25/17 1:01 p.m.

IMHO, step 1 is to put in the 1.8. Everything is 10% better with a 1.8, the conversion is easy, and while it's true that with turbos your power is ultimately limited by the flow of the compressor, having more displacement gives you more area under the curve and that's hugely useful at an autox.

Personally I'm not a fan of the Chinese knockoff turbos. That said, there's a guy on who built a car with a pair of them that's making stupid amounts of power. It's got a normal Miata-sized turbo in the normal location in the engine bay, and an enormous one that's rear-mount, with the big one blowing through the small one.

SVreX MegaDork
3/25/17 1:12 p.m.

In reply to Keith Tanner:

My downpipe, etc. is not worth saving.

Robbie UberDork
3/25/17 1:20 p.m.

If you're making up your own manifold, might want to look into stock Volvo and Saab turbos. They make some pretty big ones and they are Mitsubishi so probably better manufacturing than eBay knockoff for similar prices.

Td04- i think is the exhaust housing (wrxs use td05), and then the compressor housings come in a few sizes 13,14,15,19, bigger number means bigger compressor.

Subaru would be good used to pick as well, but they have goofy exhaust flanges that would be hard to fab.

There are also the diesel holsets, hx-35 would probably be the cheapest and easily big enough.

I am no expert but I did sleep at a Holiday inn last night.

SVreX MegaDork
3/25/17 1:20 p.m.

The 1.8L will lead me to a different set of decisions...

I have (2) 1.8's. 1 on the bench, and 1 in a perfectly good NA Miata. With a leather interior, 6 speed, and a factory Torsen. Which I bought really cheap.

I could take the Mumpkin to the Challenge for one last shot, or I could build the 2nd car. In some ways, it would almost be easier to begin from scratch (and my budget would work better). But I really don't need another stripped out car sitting around.

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