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Thinking on a k24 7400 thoughts?

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16K views 51 replies 19 participants last post by  elaw  
#1 ·
I love the big push of a big turbo, but in city traffic kinda sucks. Plus, I have been fighting some surging issues with my homebuilt hybrid t4/k26. So I thought, after driving my cousins 7a turbo with my old k24 that this is kind of a fun car, way fast boost, but peters out on redline.... What to do.... Couple guys here in utah have been raging about the volvo s60r turbo.... What have I got to loose? If I don't like it, I can just sell it and go with a gt35 or gt40.
What are your thoughts on this turbo?
 
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#3 ·
THere is a big difference between the k24 7000 and the gt35r! Just get a 3071r or a 3076r and see if that is a good inbetween turbo. I love big turbos, but a regular 35r is too big for even me. You must billet the turbo for it to be streetable. I think the 3071r would be a killer turbo for what you want..
 
#4 ·
I loved the 7400, but if it was small chassis car I think you could go bigger if you're "big turbo guy". I really loved the powerband...it's sort of outrageous....s60r had a maximum torque which was 1900-5500 rpm....yea not a single rpm...they officially quoted A RANGE. For the UrS it was great because it felt like a really nice v8. I would do it again because I love me a broad range...especially with the slow shifting audi boxes it comes in handy and the next 20vt I build will probably be for a hill climb which needs the torque. It's also a cheap option too which is great. But if you could budget for a hta 30r or something i'd probably do that for most purposes.

It's basically a efr 6255 btw.
 
#8 ·
Well here's some food for thought... my Saab 9000 Aero has an engine with pretty similar specs to the AAN - 2.3 liters, 4 valves/cylinder, torque peak at ~2000 RPM, 225HP a little below redline.

That engines uses a Mitsubishi TD04HL15T-6cm^2 (aka TD04HL15T#6) turbo, I've got it tuned to run 22 PSI boost from about 3000 to 6300 RPM, and it pulls like stink over the entire range. It spools at a little lower RPM and a lot more suddenly than the K24 - floor it from 1500 RPM and when it hits 1900-2000 it's like you got rear-ended by a freight train. And then the front tires break loose... :D

You might even get the Mitsu turbo to bolt to the 20VT manifold with a little creative enlarging of holes, although the outlet is different and it's got an internal wastegate. A manifold designed for a T3 would probably work even better.

Saab used a very similar turbo on the 9-5 Aero (and later on all 9-5s), the difference being the 9-5 one has a little smaller exhaust nozzle size - 5cm^2 instead of 6. I'd expect that turbo to spool a little faster but not work quite as well at high RPM. It also has a circular vs. rectangular exhaust inlet, although it's not clear whether the bolt pattern is actually different. There are some photos on this page: http://www.saab-tuners.com/en/trionic-7/td04-turbo-faq
 
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#9 ·
Volvo also used to use the td04 18t, then switched to the 7400 for the 04+ s60r...that should say enough. I also had an aero and loved it, and was looking to do a td04 but when I found out about the new k24 it was a no brainer...oil and water lines bolt right up and the exhaust housing swaps easy enough. I wouldn't doubt the 7400 has the best wheel designs for a small frame turbo out there...and you can make it better with the available billet wheels.

The td04 was a great turbo in it's day...but the k24 7400 is in a whole 'nother league. I know for a fact I would have smoked my aero which was running 17psi...and the UrS had 600lbs to make up for and was only at 19psi. Imagine the td04's power range but going on to the 20vt's 7200rpm redline.
 
#11 ·
I am so think ing about doing this, but I did finally sort out my issue. The MAF sensor that I was using was getting messed with surging. I changed my map back over to speed density and amazingly the problem is gone. I still think I might get this as a better daily driver turbo. I found two that aren't badly priced, more than my cheap ass wants to pay, but still not bad.
 
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#12 ·
Hey guys - after a successful rally in groff's 90, I'm looking into the 7400 for it's top end support. It's bad enough we're running a stock k24 7000 on a chipped ecu, but factor in the massive heat of rally racing and the inlet restricter, and we're left with pitiful boost levels...

What's the scope of putting the 7400 into a K24 7000 hotside?

Also - what's the skinny on upping the turbo, but still running it on a chipped ecu? I can see every reason why this wouldn't work, but since I haven't heard of any experience, I want to ask the question!

Thanks guys!
 
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#13 ·
I think that a porsche k26 housing is what you need, but I am sure a machinest could open the stock K24 housing up to fit. Also ATP has some 8 and 10 K26 housing.......
 
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#14 ·
I would think that putting the 7400 into a 7000 hotside would just be a matter of machining it considering the fact that you can put a 30r or H1C/hx35 in a k26 hotside with a machine job.

The main issue I see with putting the 7400 on a regular chipped ECU is the fact that the 3b injectors are MAXED out on the top end at anything more than 15 psi. I know this from experience. Injector upgrade at a minimum, the MAF might be able to handle the rest with a few small tweaks to the fuel map maybe?
 
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#19 ·
I'm wondering if the 7400 would be a good canditate for a CIS 10v thats pushed hard. The reason I'm asking about the high pressure ratio is you would need it in order to make up for the pressure drop across the metering plate and crummy intake tract.

At say 5500 rpm I bet your lucky to see 12 psia at the turbo inlet with 17 psi turbo discharge pressure. Thats a pressure ratio of 2.6 (ok for a k26 but off the map for a K24), at 20 psi thats a pressure ratio of at least 2.9
 
#20 ·
Ah in that case, I would would bet it could do it. I was thinking of a 20v, where on both turbos would be just about flat out, and while the compressor might be relatively efficient at that stage, you run into problems with the hot side and the fact the center section doesn't like it. RS2 seems to have a beefer center section not surprisingly. Also that pressure ratio on a 20v is a whooole different story than on a 10v.
 
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