As for headers, you can get some custom made but they are not cheap. I went from HX30 with stock manifold and exhaust to headers, BW s200 turbo and 3" exhaust and the top end came alive like crazy. I still think headers probably aren't needed for our power levels but the US 603 manifold was awful.

Are you intercooling?

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I just think the headers are good to do while the turbo is off anyway, and I'm just a fan in general. Plus it seems like a nice place to mount an EGT probe.

For the exhaust, I guess you went the custom route? How does that work, will any muffler shop just run pipes from the headers back? I would definitely add a muffler back in, and maybe a resonator. I don't want TOO much noise and definitely no drone.

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I do have an intercooler, it's 27x9x...3 I think. There lies the benefit of huge SDL bumpers! Anyway, I made my exhaust myself, it's a 3" with just a Thrush Hush muffler. It is surprisingly quiet, like not really any more loud than stock, at least from my driver's seat perspective. I may have some drone around 1700 but I am 98% sure it is because the downpipe vibrates on the body from time to time. Still need to fix that.

If I had to do it again I would probably take it somewhere for the exhaust, but I really wanted to weld. I made it so the downpipe can be removed easily should I need to swap turbos, etc.

Did you do that mainly for more power, or did you think it was needed because of the bigger elements? I keep hearing conflicting opinions - generally, US folks seem to on the very conservative side of things, thinking you need a huge intercooler or you're gonna melt pistons, while the Euro guys (who do this a lot more) seem to take more of a "don't worry about it" approach. Of course, it's easy to be cavalier about a stranger's engine on the internet.

Ideally, I would like to intercool, but there's just such limited space on the W124 - I guess a could fit a tiny intercooler somewhere, but then is it even doing anything?

The bigger issue is actually my complete lack of welding and fabricating skills - so I have no ability to weld brackets or whatever to mount the thing or, more importantly, any way (that I know of) to run the intercooler pipes into the intake manifold.

I'm just kind of hoping the bump in fueling is modest enough (plus this whole shorter injection duration thing, with no late burn) that the IC won't be needed. I'm not looking for crazy power, just want the thing to run better - and Dieselmeken's pump actually worked out cheaper than a rebuilt stock unit. I mean, obviously I want some extra power, but I mean I'm not trying to break any records on STD. Leaving that to the Finns.

In any case, most of my driving is on twisty backroads. No real hills to speak of, rarely able to exceed 60mph. Interstate driving once in a blue moon (and I have other vehicles for that, too). So also hoping relatively light loads will keep EGTs down.

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I did the exhaust mostly for power, and the IC for insurance. I think you'll be happy with 90cc, especially if you keep a smaller turbo. I have a lot of lag but off boost torque is still good, but in a w124 it would have been even better. Fwiw, with my hx30 and no IC my intake got pretty hot, with the IC it is always is cool to the touch. I recall GSXR had 6mm elements with 79cc in his w124 and with stick everything said his EGTs were fine up to about 90mph when full throttle. So...with your style and better elements, the EGT should be fine.

My HX30 delivered very good power up to 3000rpm but then fell flat on its face. My new setup is slightly better than stock up to 2800 and from there it is arguably fast.

I have a ton more thoughts to write, maybe more tomorrow.

Thanks for the info! That's reassuring. I'd be happy to hear anything else you have to add on the subject - glad to see there have been other people doing this sort of thing. A lot of the threads I've come across just predict doom and gloom if one strays from stock.

So why do you say a smaller turbo is better - less lag, right? I was under the impression that a little more flow was needed to keep up with the extra fuel. I was considering having my T25 rebuilt with T28 internals, just because it would keep fitment simple, and should move more air without being laggy. I know a lot of people recommend the Holsets, but I don't think it's the right choice for me - it seems like it's easy to go too big with the Holsets, and my build is pretty modest in terms of power.

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Why all the guesswork? This is simple math. Or just do what tomnik says. At 90cc you can melt things.

Basically you decide on power level, pick a bsfc and see how much fuel you need for your desired power level at whatever target rpm.

Then you figure out how to cram enough air into the motor to burn that fuel without melting the motor. Practically this should be 19:1 afr but you can get by with 17 or even less unless you do land speed racing or live in the mountains or pull trailers. 17 is safe under all conditions but a bit warm egt and a bit smoky.

So if you want 200hp and the motor has 5 cyl and each cyl is 500cc for 2.5l displacement, then at 4000rpm it moves 2.5L 2000 times per minute or 5000L of air at stp. Air density is 0.0765 lb/cu ft (assuming map is in lb/min). 176.573 cu ft is 5000 L. This is 13.507 lb/min.

The volume of fuel you have is 90cc per 1000 injections per injector, and 2000 injections per minute times 90/1000 = 180cc/min times 5 cylinders is 900cc / min. Density of diesel is 0.835 g/mL. 751.5 g/min. Times 17 is 12775.5 g of air/min required, for 17:1 afr. This is 28.14 lb/min.

So your motor requires 13.507 lb/minute now and when you are done it will need 28.14/13.507 or 2.08 times more air after you increase fuel to 90cc. This means you need a density ratio of 2.08.

Getting that density ratio means you need a pressure ratio of more than 2.08. How much more depends upon your compressor efficiency from the turbo map and your intercooler efficiency, if any.

Max compressor efficiency is typically 76-78%. You need a compressor where the required volume and required pressure ratio land in a high efficiency island on the map. In your case, this will almost certainly require a bigger compressor than you have. If no intercooling, you are going to need over 3:1 PR as a WAG at a "mass" flow of 28 lb/min. Probably closer to 4:1. Take home here is that pressure ratio does not equal mass flow. You can calculate the density ratio at any pressure ratio with the compressor and intercooler efficiencies, using a spreadsheet.

If your motor rarely sees 4000rpm, repeat above calcs for 3000 rpm and pick a compressor for that mass flow. Probably 21lb/min. You ideally would graph a variety of rpms across the range and see how they fit on the turbo islands.

So go find a map and a turbo that will do this. For your sort of squirty driving, pick a smallish turbine housing. Your target backpressure to intake pressure should be about 1.5:1.

That is what I learned about this when sizing up compounds for my 606. Dieselmeken selks a lot of high fuel pumps that will make huge power at huge egts. This can ve done for short periods of time without melting your motor. He would maintain that it is impossible to use 150 or 170 or 200cc fuel8ng for more than a few seconds on a public road, but your power level coukd be used for extended periods on long grades, so you should definitely have an egt probe in the manifold. I think they even have wireless bluetooth ones now.

Have fun.

Karl



Sent from my SAMSUNG-SM-G935A using Tapatalk

Here's a mess of my other thoughts, which are all pretty unscientific but, oh well

- The Holsets are tried and true in some cases, but for people like us there is no good match. For example, an HX35 is fine for 300-350 hp, but an HX30 is only good for maybe 240 and the HE221 is good for maybe 260 but it has a small turbine, which brings me to a pet peeve:

- Compressors and turbines. I saw barrote on STD mentioned that boost is not as important as the amount of flow the turbo makes. This is very true and seems to be ignored by most on there. You really don't need a lot of boost or flow, most people over do their turbos and neglect the turbine side of things. You see people getting HX40s with HX35 turbine wheels and some little 8cm housing. If you want power, you need these engines to breathe, especially the 602 and 603 since they have less valves. Putting a turbo that can flow 55 lbs of air when you only need 40 is a waste and likely results in lag. Having a small turbine housing to make it boost sooner just makes you lose power in the upper rpms from backpressure.

- The trend nowadays seems to be getting a pump set for 160cc and aiming for 400 hp. People are saying you need 30 psi and huge turbos to do this. It has been shown over and over by some Finns that you don't need this much, muuris made 381 hp from 110cc and 27psi and 400 from 130cc on a 606. Dieselmeken made 355 with an HX35 and 120cc on a 603. One guy made 330 from 120 or 130 cc on a 603 at just 19psi. Sure it's cheaper to just get a higher cc pump than get manifolds or proper turbos but then you are just wasting fuel and probably smoking a lot. The reason people think that big turbos make their cars faster is really because the turbine wheel and /or housings are bigger. On the flip side, a turbo can only make as much power as the lbs it can flow so cranking up the boost on a small turbo doesn't add any more air past a certain point. And putting a huge compressor on a small turbine doesn't help much because now you are spinning the turbo even slower to make the same air and the turbine can't scavenge as much.

For your build I would say somewhere between 18-20 psi should be fine, and a turbo that can make 30-34 lbs of air at 70% efficiency. Usually when a turbo lists the max airflow it will be for 68-70% efficiency fyi. I am running 19 psi on my 603 with 90cc and no smoke. You may require even less because of the bigger elements.

So anyway, a lot of this is max power talk and like you said, you are more twisty road driving so you can probably ignore a lot of it. I don't necessarily agree that a small turbo is better, but if you don't ever plan to run it in high rpms then there is no reason to lose low down torque. I thought everything was great for a while with the HX30 but once I swapped it out it was like night and day. I would not recommend getting that turbo, it has a big turbine and compressor but really doesn't flow much for its size and the turbine housing is tiny. The thing was screaming at highways cruising speed.
I think your manifold is t25 vs t3 so if you get a different turbo an HE221 would fit, or perhaps a TD04 or TD05 from Mitsubishi. If you get a custom manifold then of course you can get whatever flange you want. If you decide to skip the exhaust you could possibly just have a shop make you a bigger downpipe with a vband attachment so you can attach different turbos in the future.

In the end, do what you want, just the pump alone will make the biggest difference, the rest is really just fine tuning. You may decide you want to take it further in the future! I would definitely recommend getting the turbo upgraded or finding a similarly sized more modern version. And stay away from any turbine housings that are less than 7cm / .48 ar. (although in your case with a 5 cyl a 6cm will probably be fine)

Here is a somewhat relatable thread:
G-wagen , om605 , 6mm , holset

Also muuris has a lot of good advice if you browse through his posts.

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Dan
2005 E320 CDI - 246k
1987 300SDL TD05-16g, Herlevi pump, Elbe manifold, 2.47 LSD - 213k
Past: 1987 300D - 264k

Thanks for all the info, guys. You've given me a lot to think about! The turbo I'm thinking about utilizes the stock T25 housing, but upgrades the turbine and compressor wills for increased flow. I'm still looking for an exact compressor map, but I found one that I think might be right that shows mass flow rates in the upper 20s/lower 30s at 70% efficiency; max boost is around 21psi - might be right on the money. Trying to get bona fide maps from the turbo builder to make sure.

I guess my big question is, do I need to do all of this stuff together? I mean, obviously it would be ideal to do the pump, turbo, headers, and exhaust in one shot - but it would be easier on the wallet to space things out a bit. would it be worthwhile or safe to just do the pump first, and then continue on from there?

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You can put the pump in and just not connect the alda, I did this for a few months and it wasn't bad. Usually the pumps come set in the upper 40s for off boost max fuel, so essentially the same as stock when at full throttle with boost. It will probably be a bit slower than before but barely noticeable. I am not sure what the 602 ip setting was stock. 603 was around 50cc max, so it may actually still have more power for you than before.

Apparently my pump has an externally-adjustable ALDA unit - I don't know exactly how it works or how easy it is to adjust, or even what the adjustment range is - but I may be able to keep the ALDA connected and just turn it down to 50cc or so, until I do the other upgrades.

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Of course you can make power at AFRs from 12:1 up to 19:1. That is no secret. The question is whether your EGT will melt your motor at the lower AFR ratios. This is dependent upon heat soak and duration of full power output. If only drag racing, and smoke is not a concern, then 13:1 is probably a great AFR. If you want sustained high power output, then 17:1 is the lowest you will want to go.


A density ratio of 2.08 is required for 90cc fuel and 100% VE in this motor. If VE for a two valve motor is 0.75, then the density ratio required is 2.08/0/75, or 2.77. The pressure ratio required to produce this Density Ratio without any intercooling is 4.88. With intercooling of 75%, the required Pressure Ratio would only be 3.12. This is 32psi of boost.

You would therefore need a compressor that will flow 28 lb/min at an intake pressure of 32psi. Anything less than that will give you an AFR of less than 17:1. Spreadsheet for this from Bush65 is over here:

https://docs.google.com/spreadsheets/d/1R10KVT5v79f6Ula7_mJTlb0uLmc8rof22X03Fz6_u5Q/edit?usp=sharing

Just heard back from the turbo shop. The setup I'm looking at flows 34lb/min. Should I be asking about pressure or density ratios? Or can that be calculated? Sorry, can't open your link right now because of firewall at work.

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