rear mounted turbos?

[murran]

hi you turbo guys. im looking for cheap way of turboing my e21 325i. im not after any amazing hp figures (200 maybe) and want to keep the motronic as it is (maybe a chip change).
i have some ideas about a not obvious turbo install.
ive started a thread on trampdrift about it.
http://www.trampdrift.co.uk/Forum/TD/sh ... #post16863
could you please have a read and tell me what you think?

[Gunni]

rear mounts are a bad idea and alot more difficult then normal setups.

Also , do you want something that works real well or something that works bad and get´s you internet fancy points?

Also there is no use in doing a turbo conversion if you just want 200hp.
Rather a 30hp N2O shot .

[murran]

well the e21 problem is this servo set up. and rack u/js being in the way.

ofcourse if it was l/h drive i wouldnt have this problem! and could do this.....

or this....

very easily.

what im proposing isnt really a rear mounted affair but put it at the back of the gearbox here.


where the two front pipes come past the gearbox, put them into 1 with a y piece then a short flexi section. make and weld a mount for the turbo on to the gearbox cross member make up some inlet pipes to run inbetween the gearbox and the tunnel. shape them and maybe flatten them a little, make up some brackets etc. so i can mount them on the gearbox. samco hose to the airflow meter. and on the pressure side to the throttle body. workout an over boost system (actuator) to make it 0.3-0.5 bar. pumb in a dump valve......

[Gunni]

N2O setup and you don´t have to worry about any of that crap and it will be cheaper.
Easily sellable if you head into another direction.

What is the space below #1 cylinder like?

get a filter relocation kit and you should be able to run a front-bottom mount setup.

[murran]

there is space in that area if i move the filter as you said, but not much. would be a tight squeeze tbh and not really a good idea i think, got to run the air pipes across the front etc .
where as if its just behind the gearbox id just need to run them up the n/s of the gearbox which there is room for.
i know what your thinking, but im not wanting to do it this way just to be different.

where would be best to take an oil feed from? oil pressure switch take off? i can braze a return in the sump quite easily as its an e21 tin sump i put on the 325i lump.
is it "possible" (not is it best) to run 0.3 to 0.5 bar using the standard motronic and make 200bhp on a standard facelift 325?

[Gunni]

It´s very possible and been done tons of time.

If you mount the turbo by the gearbox you´ll need a oil pump to pump the drain from the turbo to the sump. Otherwise you might be looking at clogging up the drain and building up to much pressure.


I´m pretty sure there is space there below the #1 cyl for a tinky T3 turbo which is what you´ll want to run 200hp.

[mattrs]

There was a rear mounted turbo (where the silencer should have been) on a 205 gti featured about a year ago in practical preformance car. From what i remember they said it worked quite well! You may be able to get a back issue if its of interest.

[e30topless]

murran,
a freind of mine has a turbo'd e21 rotting on his drive.

it's really quick but keeps sh!tting gearbox's give me a shout if you want to go see it ! he's always happy to help out

[GeoffBob]

Murran,

What you are proposing is a lot of work. One of your major obstacles, as Gunni mentioned, will be getting the oil from the turbo back to your sump. Any time the turbo is at a height lower than the sump it has nowhere to return/drain its oil to, and therefore will require a pump. Combine that with all your other hoses, fitments etc and I question if you will have enough room behind your gearbox.

There is also a very sound technical reason to locate your turbo as close to your engine as possible, and that has to do with heat loss from your exhaust gas. In short, you need to keep your exhaust gasses as hot as possible to ensure the best possible exhaust gas velocity, and therefore do the best job of spinning your turbine! The longer the path between the engine and the turbo, the cooler the exhaust gasses (and thus the slower the exhaust gasses) by the time they arrive at your turbine.

If you are serious about this idea then a) consider an "Aerodyne Aerocharger" as your turbo of choice since it has a self contained oil reservoir around it, and thus will not require you to deal with oil pump issues, and b) lag (themally insulate) the hell out out of the exhaust pipework with layers of heat-wrap, between the engine and the turbo, to minimise heat loss from the exhaust gasses, and thus maximise your exhaust gas velocity..

[murran]

murran,
a freind of mine has a turbo'd e21 rotting on his drive.

it's really quick but keeps sh!tting gearbox's give me a shout if you want to go see it ! he's always happy to help out

i take it its r/h drive? is he splitting it?

[murran]

running a low boost i dont think im guna have much problem with the gas velocity slowing down. i can always channel it into a slightly smaller bore exhaust pipe before it goes into the turbo to speed it up.
well ive had a read of this i found via google........
http://www.rbracing-rsr.com/oilsystems.htm
interesting, i do need an oil scavenge pump in the return line. £200 odd quid is abit much i think.
looking for a cheaper alternative..... do you think this will be able to handle the oil temps......
http://cgi.ebay.co.uk/ESTIMA-LUCIDA-OIL ... 2a02525c16

[Gunni]

Your going down a dead end street continuing this.
If you do make it work, it´s never going to be worth it for the hassle it brings and the cost.

[fuzzy]

there isnt really a need to reinvent the wheel when the current design works so well.

[murran]

but it going to be simpler and less hassle.
guna get another pair of front pipes to cut up. ive got an audi a4 1.8t turbo at work i can have for free. ive already got some 8mm thick steel to make some flanges out of to bolt onto the exhaust sides of the turbo. theres some lengths of exhaust tubing at work i can make inlet pipes from.

im not reinventing anything, people have been doing this for years! especially in america.
ppc did it a while ago on a pug 205 1.9gti
http://www.balancemotorsport.co.uk/main ... roject+Car
went from making 121bhp to 176 on just .5 bar. and that was mounted right at the back, not just past the gearbox like im on about.

i suggest you read it before saying "re-inventing the wheel blah blah"

[fuzzy]

im no e21 expert but wouldnt it be easier to use a remote servo and turbo it the conventional way?

[murran]

no it really wouldnt i dont think. and would involve me buying expencive things i dont already have!
right im going to start fabing up pipes etc then when ive got the cash im getting this as it seems well recommended and used by lots of folks for this very job.
http://www.merlinmotorsport.co.uk/p3652 ... _info.html

[e30topless]

murran,
a freind of mine has a turbo'd e21 rotting on his drive.

it's really quick but keeps sh!tting gearbox's give me a shout if you want to go see it ! he's always happy to help out

i take it its r/h drive? is he splitting it?

yes it's RHD doubt he will be breaking but you never know, it's apparantly a 'famous' car in the e21 world ?

your welcome to go have a look/chat he's a decent guy

[e21Jason]

I guess he has a white e21 with lots of badges as well as Kam's old turbo

Jason

[GeoffBob]

Your going down a dead end street continuing this.
If you do make it work, it´s never going to be worth it for the hassle it brings and the cost.

+1

Murran, you are talking to people here with years of experience in doing what you are trying to do for the first time with no experience.

Regardless of what level of boost you are running, heat loss from your exhaust gas will lower your gas velocity. Narrowing your pipe will regain the lost gas velocity, but at the cost of reduced flow area and thus increased back-pressure. Your engine will effectively have to work harder to drive the turbine in order to overcome the energy lost to the radiated heat. You cannot recover energy lost from your exhaust gas by narrowing the pipe. Once that energy is lost its gone for good!

What you are proposing will work, eventually, but at what cost? Apply your mind to how to relocate your brake servo to give you the space your require for a proper turbo manifold, and you will be able to implement a tried and tested solution that will deliver superior performance and increased practicality, without wiping out your boost pipes each time you drive over a speed-bump.

[Gunni]

People are telling you this because they know...

I swear to you Murran that the issues needing solving are way more then moving the brake booster
or hell just go manual on the brakes, it will work if you size them right.

Here is your setup.

The length of pipe from the engine to your turbo will loose heat. The heat will lower the turbine speed. That means the difference in turbine rpm´s from no boost to 0.5bar boost are higher, by alot.
This will create LAG, and this will create a high boost threshold despite you running a small turbo.

I have seen those camaro´s with rear mounted turbos, they make boost at 4.5k rpm , and revlimit at 6.5k , so that´s a an enhanced powerband of 2k rpm. That´s so not worth it.

I´d reccoment a supercharger if I´m to be honest over a rear mounted turbo.

Even if things are done on the cheap, that doesn´t mean the gains are worth it.

[e21Jason]

Murran if you need 200bhp is a m20 2.8 build or a m52 swap not easier cheaper, also you could run the hydrualic brake setup from an e28 which uses the power steering pump to pressureise a hydralic booster


Jason

[murran]

a strokers not really an option when the cars used for drifting now and then. they dont really like high revs. m52 convesion is cheaper than a £140 pump and a few oil pipes making up at a hydraulics place and is less faffing about than cutting up the exhaust and making some inlet pipes?

the heat loss thing i see what your saying hot air expands as it goes down the exhaust it cools and contracts taking up less space so moving slower.
between the manifold and where i want to put the turbo i bet its only lost 15-20 degrees. at temps around 230-250 degrees a 15 degree loss isnt guna make much difference really is it?
i have one of those laser temp guns at work to check if you want? can get the car hot, blast it round the block a few times, jump out and check the manifold vs back end of the front pipe (where i want to put the turbo) difference?

its very true, i dont have much experience at building a turbo system from scratch. but ive been a mechanic for 10 years and an mot tester for 5. i work around excisting turbo systems quite alot, changing them, diagnostics of boost faults etc. mostly vag stuff.

[GeoffBob]

Murran,

It's the heat loss from the exhaust gas that you are concerned about, not the heat loss from the actual pipe (although the heat obviously travels from the gas to the pipe to the surrounding air). As a result, an IR temperature probe won't be of any use to you. To measure correctly you'd need two EGT probes, one as close to the head as possible, and the other just before the turbine inlet. You'll likely see a drop in gas temperature of around 150'C to 200'C in the gas, but not much in the pipe itself. Also, don't confuse temperature with heat. The "heat capacity" of steel is way higher than the exhaust gas, so the temperature of your pipe is not an ideal way to gauge the loss of heat from the gas (although it can be inferred with a fair bit of banging away on a calculator).

Having said all this, I go back to what I said in my first post. If you are dead-set on doing it this way then simply lag your pipes in thermal heat wrap. Basically it prevents the loss of heat from your pipes, and by raising the temperature of the pipe (as a result) is reduces the heat transfer from the exhaust gas to the pipe! Simple physics and reasonably effective, and won't cost you an arm and a leg.

Also, if you can, seek out an "aerodyne aerocharger". It's a turbocharger with a self contained oil reservoir around it, so you won't have issues with oil having to be pumped to and from the engine. This will be your major technical challenge IMO.

Be warned about using an electric oil pump if you use a conventional turbo. I have an electric water pump on my track-car (in place of mechanical) and if it fails I have numerous warning mechanisms to tell me to get the hell off the track before she overheats. You won't be so lucky if your electric oil pump fails. Turbo’s die in a fraction of a second when starved of oil while making boost. I would suggest that you use your engine oil pressure to pump to the turbo (as normal) and simply use the electric pump to scavenge the "drained" oil back to the engine sump. But exactly where you will drain that oil to from turbo I don't know? A "mini-sump" under the turbo maybe? Do you have the space for that? Remember, oil flow through a turbo must be vertical (top down)? And if the electric pump fails the oil will have to back up somewhere? OK, better a cloud of black smoke out the back than a damaged turbo, but I still think you will have issues building a "mini-sump" (catch-can) for your turbo. On the other-hand, following this method, if you spring a leak between the engine and turbo your engine will eventually empty its oil all over the road.

Assuming you can handle all these challenges then I say good luck to you. I don't see this as the best way forward to turbo your engine by any means, but if you have all the parts lying around as you say and you're just out to have a bit of fun without breaking the bank, then what the hell. If she blows up you won't have wasted a whole lot of money. I know people who spend a fortune, and still manage to blow them up. Still, think it through carefully.

Regards

[fowler]

Just supercharge it it has been done on a e21 have a look on fritzs bits website kit supplied by A-tech have a look in the traders section. Rear mount turbo's
ARE GAY !!!!!
for more info have a look at rotrex superchargers less pipe work etc

[Boyraceruk]

I'm with Murran on this one, by the looks of it all he's buying is an oil pump. If the turbo dies it has cost him an oil pump. Who cares about where the turbo is making the extra power if it costs so little?

M52s cost money, M20B28s cost money, superchargers cost money. Either come up with a better solution using that turbo and a bare minimum of costly extra parts or work out why it won't make the car quicker.

[drew555]

Assuming you can handle all these challenges then I say good luck to you. I don't see this as the best way forward to turbo your engine by any means, but if you have all the parts lying around as you say and you're just out to have a bit of fun without breaking the bank, then what the hell. If she blows up you won't have wasted a whole lot of money. I know people who spend a fortune, and still manage to blow them up. Still, think it through carefully.

At least someone's being nice.

He never asked if it was a good idea, he's gonna do it anyway, so the naysayers should really clear off and find another thread to troll and leave the people with genuine, useful advice here to help a brutha out.

Yeah, there are more conventional ways of doing things. He'd get more power from an e46 M3 engine swap for example, but he's making a turbo'd E21 out of bits of crap he's got laying around.

If he had a turbo manifold laying in the yard, no doubt he'd use that, or a supercharger (I think I may have one of them in a drawer in the kitchen... gimme a sec.. nah, it's not, it's a peg).

I for one salute you Mr. Murran, and wish you all the luck in the world.

And here was me thinking that the zone had changed.

[GeoffBob]

At least someone's being nice.

Thank you Drew, that's because I'm a nice person

If he had a turbo manifold laying in the yard, no doubt he'd use that, or a supercharger (I think I may have one of them in a drawer in the kitchen... gimme a sec.. nah, it's not, it's a peg).

I bet TurboBrown has a supercharger in his kitchen drawer

[toby]

I admire your creativity and determination. I'm not being critical here as I'm not in a position to take that stance. Have a go at the rear mounted turbo. You obviously want to try it. Besides the technical inefficiencies and location issues there's another factor to be considered in controlling it all. If you do decide to mount a rear turbo just to see how it works and to keep running motronic, there's a fair amount of money involved in mapping it correctly and I would imagine it to be more costly than a conventional set up. A more unconventional set up would have less known values to extrapolate air/fuel calculations from and limited adjustability. I'm just mentioning this as you mentioned 'cheap' as your outlay for the turbo set up. If it is cheap to bolt together and find the parts but costs a fortune to get running right it would be a pain. Have you had any ideas on your budget for mapping?

[Gunni]

Who cares if the turbo was free?
He needs oil lines, charge lines, intercooler, hoses,

There IS space below #1 for a turbo. That in itself would be so much better.

[murran]

im after 200bhp.
i could do it with a cam, billet rocker and a posh exhaust manifold..... cost £1500 minimum.
m50 conversion...... £750 at a guess.
b28..... £750 again id guess.

id like to fit a pedal box if im honest. theres people on e21.net that have modified mk2 escort ones. but theyre £220.

had the car on the ramp today after work. offered the free tt turbo up to the car, the in and out on the air side wont be in the right (read "ideal") place with the exhaust in and out where i want them.
the main reason i dont like my idea is the turbo being under the car getting splashed with water mud and sh1t all the time. that and you cant look at it with the bonnet off!
shall i just buy a pedal box when i get paid insted of that pump???? then think about turbos.

[Gunni]

You don´t need pedal boxes. Your car already has it from the factory.

To go boosterless you need to resize your master cylinder to adjust the brake feel.
It will never be the same as it is now. But the feel will be better, it will be more modulatable
and you can design it to be adjustable.

If you want more details on boosterless brake setup then start another post about that.

But if we assume you´ve gotten rid of the booster then your space to create a much much better turbo setup is now available.

[fuzzy]

At least someone's being nice.

Thank you Drew, that's because I'm a nice person

If he had a turbo manifold laying in the yard, no doubt he'd use that, or a supercharger (I think I may have one of them in a drawer in the kitchen... gimme a sec.. nah, it's not, it's a peg).

I bet TurboBrown has a supercharger in his kitchen drawer

i have a t34.63 in the cupboard.

[murran]

on the mapping side, i was guna try running low boost and see how the motronic copes with it.
i have a mate of a mate whos fitted a few turbos on v-tec civics and the like.
he says he can build me a system to back the ignition off and a separate vac fed fuel pressure reg to up the fueling slightly under boost for very little money as he already has the stuff laying around not being used.
hes even got a 1 bar max tim boost pressure guage he says he'll throw in. but hes advised me sticking with the low boost thing if keeping the motronic.

[murran]

ive seen the chaps pedalbox on e21.net if i was doing it, id want that exact set up. just looks so right!

i know what you saying about sizing the master cylinder correctly for the size of the pistons in the calipers/wheel cylinders to get the relationship between the two correct without having silly travel or too much effort from your foot.

[gcs325i]

http://www.e30zone.net/modules.php?name ... highlight=

Might be of use even though it never got finished.