Feedback wanted on a mild 2.5 build - Turbo Dodge Forums : Turbo Dodge Forum for Turbo Mopars, Shelbys, Dodge Daytona, Dodge SRT-4, Chrysler PT Cruiser, Omni and more!
Engine - General, Exhaust & Induction Topics about the general engine items, exhaust system discussed here & Improving the intake tract - air filter to intake valve.

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post #1 of 8 Old 08-15-2019, 10:14 AM Thread Starter
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Feedback wanted on a mild 2.5 build

So on the latest chapter of the longest ever 24 hours of lemons build, I'm finally thinking about the engine build. In my garage I have a common block 2.5 turbo I from a 1989 spirit that I'm using as the engine for the BMW project. I would like to build it up slightly so it's making around 200-225hp, but still be reliable. I'm trying to figure out what parts I absolutely should upgrade, and which I can leave alone to get there. I don't want much more power than that because endurance racing is hell on modified engines, and honestly 225hp in an E36 is probably just fine for what we're doing.

Important things about our goals. Endurance racing is crazy hard on engines. We are WOT a lot, for 7.5 - 9.5 hours at a time with only fuel stops as breaks. Heat management and oiling are king. We do not need crazy power, we need safe power that won't be on the ragged edge of failure. I just would like a mild bump from the stock engine.

Engine mechanicals
I wasn't going to change much inside the engine. I know fancy forged pistons are nice, but I was hoping that the regular ones would be ok for such a mild increase. If this is just wishful thinking, let me know, I'll change some budget around.

I do have a bunch of TII rods kicking around, so I can upgrade those.

I will be getting the block and head decked to make sure they're in spec for a cometic MLS head gasket as well as hone the cylinders if needed, and I do have ARP head studs for the engine. It'll get new bearings while it's apart.

Balance shafts are already out and oiling hole plugged.


Engine oiling
I have the higher flow oil pump to put in the engine that'd used in previous engines, and I have a large oil cooler off of an FC RX7. No other real changes to the system other than a stainless feed line to the turbo. We tend to run 5W-40 in the race cars.


Cooling
I'll be using the largest radiator I can stuff into the E36 with a good fan setup. I'll use whatever water pump makes the most sense for my modified belt routing (I have to move the alternator to clear frame rails, it's going roughly where the power steering pump should be with a TON of heat shielding), I have an early and later reverse rotation pump. I have the pieces already for the cylinder 4 mod, which has helped in the past, and I'll be using a 180 thermostat. I do want to upgrade the system to a more modern expansion tank setup, rather than the older overflow design, I just like it better. I think some of the E36 radiators have that built in.


Fueling
We use a fuel cell with walbro in line pump. I was going to get an adjustable regulator to be safe. All the injectors I have are the TII injectors. not sure yet if these need to be upgraded for the mild power bump.


Intake
I've cut open my single piece intake, cut out the runners a bunch, and welded it back up. The throttle body is moving to the other side to make intercooler piping easier when it's in a RWD setup. I was going to upgrade to the V6 throttle body however. The turbo inlet I'll plumb to fresh air somehow with a cone filter.


Exhaust
Not much changing. I might port match the manifold if I feel bored, otherwise 2.5" downpipe and then straight pipe out the back. If I get really bored, I might make my own manifold simply so I can mount the turbo backwards and have the cold side face the front of the motor, it would make pipe routing easier. But that is likely a down the road project.


Turbo
I have about 4 stock garret turbos sitting with various levels of wear from mostly fine to the nut fell off the cold side and everything is dead. I plan on rebuilding the best one and using that. I would like to keep turbo boost ECU controlled if possible, but I can run a manual controller if needed.


Engine management
I have an SMEC from my old '89 daytona that's been modded to have the flashable chip in it. I will be adding a wideband and upgrading the MAP sensor and updating the tune to match.



Looking for input on the above for things I should do differently or which parts are good, in order to get to that safe 200-225hp number.
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post #2 of 8 Old 08-15-2019, 02:18 PM
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Re: Feedback wanted on a mild 2.5 build

12psi netted 198hp/280ft-lbs on my 2.5 at the wheels. The head was stock with a 2 piece intake, stock TB, Ported exhaust manifold, S60 turbo, 3" straight pipe side exit exhaust, Big Cummins FMIC.

If you've got the manifold off, port the hell out of it. Also into the throat of the turbine housings, the short side radius and the rest of the swingvalve too. Also opening up the outlet on the compressor housing helps with throttle response and spool. I make the walls at the very end of the outlet about .125 all around then taper as far in as I can reach. This will smooth turbulence and help keep the heat down.

If you're going to weld on the manifold I'd put a 58mm TB on it from 99 into the 2000's 3.8 Minivan.

Cooling is the key and a good a/f ratio for those long runs as I'm sure you know. I'd run it 10.5-11 and up the boost for more power. That should keep the pistons cool and detonation free.

Keep us updated, I'd love to pull up to the local shop that races BMW's in this. :)
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post #3 of 8 Old 08-15-2019, 03:07 PM Thread Starter
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Re: Feedback wanted on a mild 2.5 build

I've never done any porting, but goodness knows I have enough spare manifolds that I can practice and screw up a few times. I'll add that to my list.

I'm very well versed in the importance of keeping things cool. The Saab 9-5 we've been racing since the death of the Daytona has been fighting us with overheating and I've been ripping my hair out trying to solve it. Part of the issue was a very lean happy stock tune that was sticking in the 14's even while boost built, which is terrifying. So yes, proper AFR and temps will be adhered to.

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post #4 of 8 Old 08-15-2019, 04:09 PM
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Re: Feedback wanted on a mild 2.5 build

biggest issue is keeping it cool

followed by not using a ton of boost on the track to get the power.



Port the water pump. port the block holes for oiling.
windage tray or scrapper or baffled pan.

you should look into PT lifters and beehive springs. makes the car much happier to rev.



I would suggest re drilling the stock manifold for standard T3 turbos. so you can just get the ebay chinesium turbos at 100$ a piece.
you can move up to a T3/T4 that will make more power with less boost.


if you redrill the manifold and use a ebay turbo you should be able to face the turbo the other way much easier.

The NECK on the 1 piece intake is the biggest restriction. cut it off and weld on a new neck facing the way you want as well. and step up to the 58 MM throttle body .


a good size intercooler and oil cooler will help the engine survive. go big or go home.


you wont need aftermarket bottom end components for 225HP. but you will either need some porting of the heads or more boost.. i would suggest porting and keeping the boost lower.

I have acute Taurocoprophobia. Achew!
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post #5 of 8 Old 08-15-2019, 08:04 PM
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Re: Feedback wanted on a mild 2.5 build

If you build it for power, you won't finish the the race.

Built it for endurance instead.

Is there a reason why you're limiting yourself to a 2.5L 8 valve engine when 2.4L 16 valve is cheap, available, and makes the power you're looking for at stock level? Knowing what I know, I'd probably just run a n/a 2.4L 16 valve engine for durability sake.
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post #6 of 8 Old 08-15-2019, 09:53 PM
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Re: Feedback wanted on a mild 2.5 build

A friend of mine used to ice race GLHT's up in Winnipeg back in the late 80's and early 90's. I would continually supply him with low cost GLHT's I would find for import to Winnipeg. He wrecked more than his share of them (lol). Anyway, this of course was during the winter in the cold. Paul Rosse would build his engines. Pretty much bulletproof at around 260 HP. Similar deal, at or near WOT for half hour or more at a time during heat races. Of all things, he was having numerous issues keeping the turbo bolted to the exhaust manifold! Car would lose boost and eventually he would pull off the course not wanting to get run over. Happened repeatedly that he would literally melt the exhaust studs and nuts right off the turbo! He must have had a significant exhaust leak between the turbo outlet flange and the turbo. That exhaust leak acted like a torch to the fasteners. So make sure those flanges are machined nice and flat and use the best grade fasteners you can buy.

Todd
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post #7 of 8 Old 08-16-2019, 09:12 AM Thread Starter
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Re: Feedback wanted on a mild 2.5 build

Quote:
Originally Posted by masterjr3333 View Post
biggest issue is keeping it cool

followed by not using a ton of boost on the track to get the power.

Port the water pump. port the block holes for oiling.
windage tray or scrapper or baffled pan.

you should look into PT lifters and beehive springs. makes the car much happier to rev.

I would suggest re drilling the stock manifold for standard T3 turbos. so you can just get the ebay chinesium turbos at 100$ a piece.
you can move up to a T3/T4 that will make more power with less boost.

if you redrill the manifold and use a ebay turbo you should be able to face the turbo the other way much easier.

The NECK on the 1 piece intake is the biggest restriction. cut it off and weld on a new neck facing the way you want as well. and step up to the 58 MM throttle body .

a good size intercooler and oil cooler will help the engine survive. go big or go home.

you wont need aftermarket bottom end components for 225HP. but you will either need some porting of the heads or more boost.. i would suggest porting and keeping the boost lower.

Keeping it cool I know I can do. The 2.2 in the daytona we got to sit at 190-200 even in august. Porting will be on my short list of things to learn, again thankfully i have many spares to learn on. The oil pan will be custom since I need to make a stepped pan to clear the BMW crossmember, so baffling will be decent.

I'll consider a different turbo down the road, but for right now I'm going to use what I have. The intake is super modified right now, and yes that restrictive neck is gone at this point. I've long known about the PT lifter upgrade, but maybe I'll actually do it this time. I know it's a cheap fast change.



Quote:
Originally Posted by tryingbe View Post
If you build it for power, you won't finish the the race.

Built it for endurance instead.

Is there a reason why you're limiting yourself to a 2.5L 8 valve engine when 2.4L 16 valve is cheap, available, and makes the power you're looking for at stock level? Knowing what I know, I'd probably just run a n/a 2.4L 16 valve engine for durability sake.
I'm sticking to the 8V for lemons reasons. I spent 5 years racing that daytona, and in lemons BMWs are really a boring choice. Throwing the 8V in it will make it interesting to the judges, and it fits my background/reputation. No it's not the best choice, but it's fine for this. I already know I can build a reliable stock engine, I did it with the 2.2 in the daytona and it ran a bunch of races with no problems until an oil cooler line blew off and my driver failed to notice. Taking the right precautions I should be ok raising the power a little. If/when I decide to move on from the 2.2/2.5 I have a saab B235r just waiting to go in.
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post #8 of 8 Old 08-16-2019, 12:53 PM
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Re: Feedback wanted on a mild 2.5 build

To me; anything besides FWD Chrysler is a boring choice, anywhere, anytime.
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