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Sensible Turbo Choice For Protege5- Questions...

Old 01-07-2010, 01:28 PM
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Default Sensible Turbo Choice For Protege5- Questions...

I have a MazdaSpeed-designed and built turbo setup, made for a P5. I have almost everything, save the actual turbo, waste gate, and maybe a few bits and pieces. Bought it nearly 2 years ago, I think I am ready to install it. My goal is to bump up the performanc,e of course, but NOT to anything close to an extreme. Something a bit higher than the MS Protege's 170 HP- say, 180-200- would be all I want. I am not willing to sacrifice much reliability, longivity or driveability in the completion of this mod. Not planning on doing much street racing, either- in fact, there is only one car I really want to spank- more on this, later.

From this site
I get the sense that a Garret T30 with these specs
Turbo Type GT30 Comp Hsg A/R 0.70 CW Trim 52 CW Dia (in/ex) 2.17/3.00 Turb. Hsg A/R 0.63 TW Trim 84 TW Dia (ex/in) 2.16/2.36
might be a good way to go. Feedback?

The same site reports the MSP as using a Garrett T25- would that be better, other variable being held close to the same? I also hear a lot about the T3/T4 turbo- what's the pluses and minuses of it, compared to both the T25 and T30?

I understand, in principal, the proceedures that site discusses to determine turbo choice, but at the moment, it confuses me. Any on-line calculators or sites that do a better job of walking one thru the sizing procedure?

Any other good choices? (Flange on the manifold is Garrett T, so other brands would be problematic.) I mean, something like a smaller-still turbo (T-20??) that might be spooled up/making boost sooner, for instance?

I know adjustable waste gates are popular, and I know the obvious advantage- adjustability- but if I WANT to "set it and forget it" and DO NOT want to run the risk of overboost, wouldn't a fixed WG be better? Wouldn't it cost less money?

If I go with an adjustable WG, what would be a good setting?

This one might call me out as a real noob, but here goes: If the manifold is set up for an external WG, but I get a turbo with an integral WG, can I just block off the WG mount? Such a turbo would be less $ than a separate turbo and WG, correct?

Set I have came with a BIG exhaust cat-back, and a HUGE can. I really am not keen on either the boy-racer look or sound of a huge can- suggestions/advice on what I might replace it with? I am somewhat old-school- an oval can with two smaller tips would be more to my liking than a single round can/outlet.

I'd like to run the stock exhaust at first, to see how I like that setup. Any worries there?

Can I possibly get by/do okay with no changes to the stock fuel injection and ignition systems?

If the answer to that is a resounding "NO," what's the easiest, least expensive, and/or least bothersome/troublesome way to go?

Atlanta test all cars for emissions- Will changes to FI/ig. change emission test results? If so, are there quick ways of covering this for the yearly inspection?

The P5 does not have an LSD, right? Think one is needed? If yes, what are good donor cars?

Any good sources for the turbo and/or WG I would need?

What about this one on eBay:
Attractive price, but I wonder about quality. Informed opinion, please.

That one car I want to beat? My nephew is currently driving an Acura. I don't recall which model- RSX perahps, but it's a bit heavier than my P5, and he's claiming about 150HP with the CAI and perhaps cat-back exhaust. (My P5 is in stock trim except 17" wheels/tires.) I was home (Lafayette, LA) at Christmas, and we went out to back roads near and beside Bayou Carencro- mostly 90-degree turns connected with short straights. On a drag race, I stepped out to a half-car-length lead off the line, but at the 1-2 shift, he took the lead by about one car length and never gave it up. Just about what I expected- the P5's shorter gearing and lighter weight got me moving sooner and quicker, but the same shorter gearing meant I had to shift 1-2 sooner, which brought him alongside me, and his higher horsepower took over from there. On the curvies, it was a different story- with him leading, I was fairly glued to his rear bumper; with me in the lead I easily kept him at a respectful distance. I attribute that to lower gearing (again), lighter weight, and much better driving skills (I've been driving longer than he has been alive...). For the re-match, I am considering mounting some very stick, ultra-low profile tires to the stock 16's. Once I have the turbo, I should be able to run and hide from him- but he's talking turbos, too...

Thanks, folks.
Old 01-07-2010, 04:17 PM
wsoape281's Avatar
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Join Date: Mar 2007
Location: houston
Posts: 1,672

run the gt25, upgrade the internal wastegate, and run a manual boost controller. the wastegate actuator for the stock turbo sucks and will cause serious boost spikes. the after market actuator will give adjustment on the exhaust side and be a more solid unit to control. the manual boost controller will give you just a little more boost control on the vacuum side. the gt25 is a good option for that power and a budget. if you want a little more power with no more boost, go with the gt28rs. the AR on the compressor side is more nominal and the turbine on the hot side reduces back-pressure a little. it frees a little power up and allows you to make more power on the same boost.

SET IT AND FORGET IT. set the boost at 8 psi and leave it alone. adjust the wastegate and the boost controller to get it to 8 psi with no spikes. that is enough boost to get you to 180-200 whp on the gt28rs and the correct supporting mods.

you need engine management. your best option is to install the haltech interceptor platinum here . install a wideband o2 sensor that you can use instead of your stock narrowband o2 sensor, piggyback the interceptor onto your ecu, install all of the other components, and tow the car to a tuner. if you talk to crossover auto, they can pre-program the interceptor with a map that will get you started.

go with a set of wrx injectors (440 cc's). those are cheap and effective. be gentle on the trans because you could easily shred gears with anything over 200 hp. get a mazdaspeed LSD since you will definitely want one. not 100% needed, but you will be glad that you bought it. the stock ignition system should be fine, just don't cheap out on spark plugs. you will be putting boost into the motor now and i have seen cheap spark plugs break off tips into the cylinder, scoring the cylinder wall to the point of needing a rebuild.

since your car is OBD II, you don't have to worry about anything other than CEL's and possibly a tech walking behind the car and smelling the exhaust. there are ways to cover CEL's, so that's not really a big deal.

personally, if you want to build this up to get some good power and not sacrifice any longevity, i would build the motor first. with this set-up, an 8 psi limit, and a good tune, you shouldn't have any issues with the motor blowing. it will, however, make the motor wear a little faster. if your car is in good shape with a very healthy motor, you should be able to confidently take the motor well over 100k miles. just remember to keep the boost down and pay for a good tuning.
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