N9T** Garrett T3 Turbo discussion

[Bean]

I've been thrown in another tangent with getting my 89' ready to resume daily driving duties with having to figure out why it's overboosting.

Could be as simple as boost lines - but I suspect the wastegate actuator. If the wastegate needs to be replaced then I most likely need to remove the motor mount to gain access.

"While I'm at it..." Syndrome then took over and I thought for a few more nuts I could swap in the Forced Performance built T3/T4 turbo off the Danielson motor I bought.

While researching exactly what the turbo was so I knew what to expect - I also started to realize it might not be what I want either (might be real laggy). I started looking for upgraded turbos that could use the stock exhaust housing.

Stock spare T3:

Exhaust: .36 AR with Stage 1 68 trim wheel

Compressor: .42 AR (Didn't bother with the wheel trim)

I know we had discussed stock AR's - but I was always referencing the compressor AR and never even thought of the exhaust housing. .36 exhaust is absolutely tiny and the stock T3 specs really are the same turbo specs that some DIESELS use.

The dilemma is that the proprietary exhaust manifold to turbo flange means we can't readily use any other turbo, but at the same point the log manifold is actually one of the nicest log manifolds I've seen. Super short runners, nice and thick with nice webbing. I also suspect it's cast inconel as the surface finish is amazing.

If a bigger .63 AR T31 housing was ever used by Peugeot they we have some options to build a pretty sweet turbo with BB CHRA, and billet wheels (Precision Turbo) - but if not the manifold needs to be modified to a T25 flange OR have a v-band flange welded onto it.

I love the v-band flange idea, but that would mean having to get a compressor housing with an integrated WG outlet on it somewhere and a v-band inlet... Found one but I don't like the downpipe / exit design.

T25 looks the most promising as the existing flange is actually very close to the T25 dimensions. Clearance issues with the turbo and motor mount mean you can't use an adapter - so the idea right how is to see if I can mill out the outside pattern of the T25 into the stock manifold - then have a stainless steel T25 flange welded in (Tig with 309L filler rod should work). Some minor porting to the new flange and then you can have a huge selection of modern turbos to choose from.

Did I mention that all stemmed from me over boosting.... It'll end up being a hole in a hose I'm sure.

Rabin

[JunktionFET]

As someone that has been positively spoiled by natural aspirated engines, I think a laggy big A/R turbocharger would be my idea of driving hell, not just on a daily driver, but on a racing/track car as well.

It always seemed like the 505 Turbos with A/R .36 turbochargers spooled noticeably quicker than the later .48 turbochargers. For day to day use the .36 was pretty alright, even with an automatic. It got especially tolerable if you bumped up the initial timing advance a couple degrees (if the engine could take it).

However, I remember back when were tuning these puppies, you could get measurably more boost pressure from the .48s than the .36s. On one of the Dani cars, it was hard to get more than about 16psi out of a rebuilt .36. It seems like boost would take an age to go beyond that.

[Bean]

Prior to this I'd always spoken of the turbo AR with reference to the compressor side only. It's only dawned on me now that the .36 AR for the exhaust is quite the limiting factor.

The 89' should have the biggest turbo offered - but again I thought the .63 AR was the compressor side - no idea what the exhaust side AR is.

That all said - If I can successfully modify the exhaust manifold to a T25, something like a Garrett GTX2860R, Precision Turbo 4828 or an EFR6258 should spool just as fast if not faster than the older T3 .36, and absolutely bury it in top end.

Eventually this will have the Dani cam and head so having the higher rpm flow capability will be important - but I want it to at least spool as fast or faster than the stock turbo.

Just need to figure out the best way to change the exhaust manifold to T25 flange now.

Rabin

[JunktionFET]

Well the 88-91s should have the .48 turbine. I say should because well... you know how these parts get mixed and matched over the years. From what I recall, N9T and N9TEA motors had the .48 pretty much universally. A few early '86 N9TEs did as well, but most N9TEs were the good ol .36.

You can look down the inlet of the .36 and .48 turbine housings and the difference in cross sectional area is clearly obvious. The .36 is indeed tiny! Makes you wonder how the engine can breathe at all even at the N9TE's stock 9psi of boost.

[Bean]

I should also mention that with all the turbo research lately I've had to wrap my head around the actual meanings of what AR and trim were - and while they play a part in turbo "size", there's no way to directly compare size between the old stock .36 AR and the newer T25 style turbos aside from flow maps.

I know how to size a turbo, and read and plot turbo efficiency maps - but they don't really MEAN anything to me - I find it much more useful to look at comparable dyno graphs of similar displacement engines running the various turbos to get an idea of how they build boost for me to really be confident in my selection.

Doing that with the new smaller quick spooling T25 type turbos mentioned and I think the car should have fantastic boost response with plenty of room in the sweet spot of the efficiency island to run all the way to redline - at the boost levels I want anyway. My goal is primarily boost response - earlier the better so that the power delivery is nice and predictable.

Rabin

[N9TE]

Isn't the whole point of the T3/T4 hybrid focusing on the intake side? I mean going at the exhaust with out integrated wastegate seems a little unconventional. I live close to Alamo (http://www.alamoturbochargers.com/index.html) and was just going to go down there with extra turbo in hand and seeing what could be done. If it's been done, they've seen it.

[Bean]

I asked the guy from Precision Turbo that was REALLY helpful in determining if there was anything they could do with the exhaust housing. His reply was that if it was a T31 or a T350 housing they could build up a new turbo with it. Pretty sure that means it has to be a .63 AR housing however according to the chart I found.

My T3/T4 looks like it was built with the .36 housing and it had a pretty big compressor turbine machined into the stock housing. From the research I did running a big compressor side on a .36 AR should make it much more laggy compared to if it had been a .48 or .63 AR housing. Machining the stock housing for the new compressor while good for easy of install, isn't really advised as they don't usually flow as well as the dedicated housing. Forced Performance did it though so I'm hoping it's decent.

After exhaustively searching for way to make the stock housing work, I've switched focus and I'm now looking at modification paths for replacing the manifold flange with the T25 flange. Stock Peugeot flange is dimensionally very close to the T25, and I think I can even angle it slightly so that the compressor housing has more motor mount clearance.

Plan is to either mill a T25 sized recess into the stock housing and weld it in, or mill 1/2" off the the entire flange and surface weld a 1/2" T25 on.

Once it's welded in place I'll port the manifold to the flange and it should be good to go. Likely look at seeing if it'd be possible to get the inside of it ceramic coated if it turns out nice and it's possible for them to do well.

In the mean time I think I'll just install the T3/T4 just to see what it's like for now.

Rabin

[Bean]

BTW - If it works - I've got quite a few more manifolds so I'll likely look at offering them up once complete and verified it's known good.

If it works - one of the new wicked fast spooling turbos should really transform the car. Best recipe I found for rapid spool was a good log manifold so that the runners are as short as possible. Spools faster than even an equal length tube manifold, and with the small turbos and the power numbers I want, it will even rival a twin scroll set up. Only down side of the log manifold is that it gives up high end flow / power. For the numbers I want - it's not even a consideration. Stand alone to take full advantage though is very likely.

Rabin

[avantgarde]

A .36 A/R housing is incredibly restrictive for a 2.2 litre engine. Turbo lag is pretty limited on the new aerodynamic turbos these days.

This is the information I wanted to know! so the flange of the stock turbo isn't a T3 like turbo? It looked kind of like the Volvo's T3 with the hump in the middle.

[Bean]

Nope - the Volvo's use the same bolt spacing as the standard T3 but it has that raised / round area in the middle that's easy to fix. Peugeot really did use a proprietary flange design, bolt spacing is smaller than the T3 and a bit bigger than the T25.

I've got a T25 stainless flange I'll either have welded on, or I'll get the the holes welded up on the ones that don't match the T25, machine flat, and install studs so that it is a T25 flange. The new Borg Warner EFR6258 is my current favorite for the turbo I want to upgrade too.

Rabin