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The time has come and I believe my stock twin turbos are going bad and so I’m looking to go single turbo. What kits are out there and which kits do you recommend?
First off, this will cost a LOT of money to do right. You can make 350hp to the ground easily with stock twins and have the car be reliable. You may want to think about finding a good used set or getting a new set of twins - that will cost a great deal less, involve a lot less effort, and still have a fun and fast car.
That said, IMHO the best way to go for a street FD is the Borg Warner EFR 8374. Immediate spool, tons of power, easily into low to mid 400's power-wise with insane response. There are a few companies out there who are making nice kits.
But, remember, with a single turbo you're also looking at a better clutch, beefed up fuel system, intercooler, good ECU, tuning, etc. etc. etc. That's where the costs get up there FAST. Not to mention needing bigger and stickier rear tires to handle the power.
I have actually done most of that other work. The car isn’t stock. I had done this work before and now to twins I have are going bad. I currently have the 99 spec twins
I was taking apart to see if the turbos had play or didn’t spin. Everything checked out but there was a fair amount of oil everywhere and this is what I’ve seen. Can’t tell if the turbos are bad in some way or just leaking
Are you doing it yourself, or paying someone? If you are doing it yourself, Do some ( a **** ton ) of research first. Im buying parts currently , and ive spent hundreds just on AN fittings, Hoses, Flanges, and other little bits and pieces that are adding up.
That's a pretty light film of oil. What is your PCV setup -stock or some sort of catch can? Are you getting any smoking?
Also the coolant hoses to the turbos are a time bomb. It looks like silicone vacuum hose, they will eventually split and rupture and the worm drive clamps that bite into and tear the hose doesn't help. OEM clamps and OEM hoses are the way to go.
It looks like you are non-sequential as well. How much boost were you running? The 99's supposedly don't do as well with a lot of boost longevity-wise.
Going from non-sequential to the 8374 you will pick up SO much response.
DaleClark:
The "we" in the old thread is my son and I,
this is his car.
I am learning with him a trying to help him sort out the problems.
We have already discussed the PCV setup, we are waiting on the catch can.
The coolant hose you noticed is actually not vacum hose, it is shinny coolant hose and has a the pink inner liner you expect of coolant hose.
We will put on better clamps.
The boost was 12psi and since the event where we found oil all over the left side of the engine its been at around 6psi based on our boost gauge and
the data out of the haltech.
While we have the turbo apart we are reseaching what else we could be wrong and what we can test.
Doesn't look that bad oil wise, if it hasn't been cleaned up. That primary intake elbow, which is now facing down, would have been a better telltale though. Looks like all the acorns on the manifolds have gone awol too.
If I'm reading the other thread correctly, you performed the comp test yourself? 70lb is bad, rotary tester or no, ideally you do it on a warm engine. Was the battery fully charged and throttle open?
Mentioning aftermarket fuel filters, there's a wide range. Some of the "racey" ones might be ok for carbs on tractors, not too flash hot for injectors.
The silicon coupler from the Y pipe to the crossover with the T clamps, not a big fan of those when you're trying to tighten on plastic, been there - suffered the leaks!
Pics of the oil was before we cleaned it. Seemed like allot to me, but maybe not unexpected by you experts.
The facing down intake did not have much oil at all.
The car was not warm and we did not hold down the accelerator when we did the compression test. This time warm engine, accelerator down, rotary compression tester.
Will take a pic of the fuel filter and post. Pretty confident it's a good high quality filter.
Had to wait for a new compression tester, the first one went bad. So the reading on the rear rotor are in the mid 90s (see pic) and the front rotor was in the low 100s.
Car was warm and accelerator held down.
We mounted the catch can in the front by the inter cooler, there was not enough room by the brake booster cause of the greddy intake. See pic.
Since the nipples from the oil filler neck come from the same single opening, what is the reason for running 2 hoses to catch can?
If we use the hose routing shown in the pic, we will remove the current hoses and plug where they go now. This should be ok, right?
Another question: If we mount the catch can on the other side of the inter cooler, we could use the existing hoses that currently go to the primary intake and re-route them to the
catch can then cap where they used to go, then remove the hoses that go to the UI and PCV value and cap where they went. This seems easier and cleaner if it will work well enough.
I'll have to post up a pic of how I have mine mounted, there is room there. I have a Stillway elbow that's larger than the Greddy.
But, that spot is just fine.
Really, you can just use 1 hose. I've always used 2 - there are 2 nipples on the fill neck, 2 on the catch can, it's just easier than trying to cap it and it gives more volume for the system to breathe and push junk into the catch can.
We did some more work in evaluating the problem.
When the car idles you can hear a subtle grinding noise in the back turbo (I think its the secondry turbo).
We took the intakes off the turbos, the back turbo had oil in the bottom of the intake again, not allot maybe .5cc.
Also took it for a drive after tighting up everything we could find, catch can installed, some wires re-soldered and we could only get 6-7psi boost.
Car was tunned for 12psi @ 4000-8000 rpm.
Also had a friend look at it who designed, built and analyzed failures in turbos in his younger years for a living.
He was able to show us that if the turbine is rotated to the right position there is play in the shaft.
Its a very small amount, but you can feel it.
We used a snake camera to look at the turbines and housing and could not see any scrape marks or damage.
Our friend concluded it likely the rear turbo has failed recently or the housing would have scrape marks.
Since we are running 1/2 the boost we should be, this seems the likely the cause of the missing boost.
This is what the forum guessed when we first started the thread.
We are thinking that since one turbo produces boost while the other does not, the pressure from the good turbo
is getting past the bad turbo and causing the blow by we found on the drivers side of the engine when this problem developed.
Question:Is it possible to replace the one turbo on the OEM turbo assembly?
If not we are going to move forwad with converting to a a single turbo.
We are looking for the recommendation of any good kits.
When you say 99, I assume 280hp turbos? If that's the case, attempting to source a second hand set to get a cartridge, if that's your issue, is going to cost a few pennies. Substituting a complete 255/265hp non abradable pair, with minimum cracking might be another way forward, as they're scrap price.The turbos can be disassembled once off the manifold.
Often find the 13mm hex inconel fasteners used to hold them together are often seized, so I'd be soaking the turbos bolts in penetrant for a day or so to minimise breakage as they're very brittle. Would still expect to snap one or two....which is where a spare set of turbos also helps.
The borescope went from the downpipe outlet I take it?
I dont know the details of the 99 spec turbos that were put on.
The shop put on the whole assembly or "cartridge".
Substituting a complete 255/265hp non abradable pair, with minimum cracking might be another way forward, as they're scrap price.
The turbos can be disassembled once off the manifold.
So your suggesting to buy a used set and between the 2 assemblies get one good one?
Before the failure the car was at 320hp to the wheels.
We want a setup that can hit ~400-450 hp, so would the 255/265 turbos be able to do that?
We know to hit 400-450 we need new injectors and fuel rail, the rest has already been done.
If you're looking for 400-450whp just go single. You "can" push twins into the 400's, but doing so puts them so far outside of their happy place that they tend to fail prematurely.
I'd say just get yourself a good EFR 8374 kit and call it a day.
I wouldn't expect 400 plus at the wheels with mazda twins - on any sort of realistic dyno.
Last set of stock twins I bought here ages ago were about $150, so yeah that's the way I'd go if trying to do it on the cheap, you get spare bolts and the copper gaskets which are unobtainable by any other means too. I'd bet 280s are probably a few multiples of that, second hand in the US.....yahoo, with a quick glance, has these https://page.auctions.yahoo.co.jp/jp/auction/n517164909, but usual BS bank, EMS, etc, charges would likely more than double that landed. Japanese did have a preference for the standard twins, if they were going to boost them significantly.
You can go to the more extreme aftermarket twin options to get to your power figure. They also go a good long way price wise to the total cost of a single conversion.
I can't recommend the internal waste gate enough. It solves SO many immediate and future problems. Every EWG setup I've seen has fought too much boost, not enough boost, torn diaphragm, broken flanges/welds, burnt through hoses, etc. etc. etc. They cause way more problems than they fix and routing them back into the downpipe well is a huge pain.
08-25-21, 08:31 PM
