Speedy88's Volvo 740 Turbo

[theo2468]

I hope I've started a trend. Especially as I'm hanging around

maybe i should post a pic up of my 940, but mine a non turbo

[jon-ovlov]

sorry chaps. realised i invited myself and hijacked the thread. my bad!!

[brickie501]

I'm getting a pretty reliable 30mpg-ish around town too, keeping off boost. More miles per mellons than the valver, that's for certain.

Interestingly it seems to be doing almost mid-way between the mpg figures for my old 940 SE Turbo estate (average 25 on petrol, 24 on lpg) and the 360 GLT (average 36 on petrol); sad maybe but I keep pretty acurate records to keep tabs on spending vs fuel money from work.

Just didn't think the difference would be that marked between 740 & 940 estates...

[Speedy88]

sorry chaps. realised i invited myself and hijacked the thread. my bad!!

Always welcome when it comes to A52-ness

[foggyjames]

Quick bump regarding turbo sizing. There are two factors which make a larger turbo make more power at the same boost pressure, and they reflect the general need to specify a turbo in two halves...

Firstly, the compressor has relatively little influence over this (as Tony's logic correctly dictates), other than that (as Chris says) if you work a compressor outside of its efficiency range, it will blow hot air. I'm not enough of an expert on the subject to say why...but it does. Hot charge air makes for reduced ping immunity, and hence less power. You can (to an extent) deal with this using a huge intercooler and/or water injection (which is what the T5 crowd all too often does, much to my annoyance), but the correct way is to choose a compressor which is correctly sized for your application...and *then* add the huge IC and WI. You can work out the suitability of a particular unit by consulting its compressor map.

The much more important factor is the turbine sizing. If you look at the turbine side of a TD04-13C next to a Garrett T4 turbine, it'll become apparent very quickly why it makes a big difference. The T4 would still be a restriction (compared with how you might spec the exhaust for an N/A application)...but the 13c is just mental. No wonder they barely make any power above 4500rpm. Of course it's a trade-off between the spool point and how well it flows at high RPM (i.e. peak power). A 3" turbo-back low-restriction exhaust will help hugely - one guy with a T5 with a Garrett GT2871R (450bhp capable?) claims his spools earlier now than it did with the original turbo (280bhp capable?) and factory exhaust.

There is a vague formula of sorts to work it out, based on the area of the turbine housing (IIRC), but I don't know the details. It strikes me as being flawed, as there are a number of factors to consider beyond housing area (wheel size and design, for example). I'm sure a book on turbocharging would tell you what you needed to know, if you were interested. In practice, it's safe enough just to copy what others have done (with dyno plots to prove their success). What I would say about turbine sizing is that I've yet to find an application where I've regretted going for a larger one (within reason). For example, a few years ago we raced a 940 with a 16T swap against a 740 with a T3/T4 hybrid, both at 12psi. It was a drag from 50mph in 3rd. The 940 pulled out a car length or so, then the 740 pulled cleanly away from it. Small turbos are very fashionable in the Volvo world, but I'm a firm believer in bigger being better (without going silly).

cheers

James

[Speedy88]

Interesting stuff, the more I learn, the more these facts come apparent. The problem I've found so far is the vast clouds of miss-information confusing the above. From my research though, the plans over winter are 3" exhaust, turbo pressure taken up to 12psi, lowerings and maybe some diff modification.

[L14MNP]

I have been saying this for some time.

Everyone needs a Turbowagon.

EVERYONE!!

EEEEEEEEVERYONE!!!!!!!!!!!!

Had one. Purpose served.



I guess I don't share the love.

[Evoman]

I know of a good book on turbos, but I cant remmeber the name....so that dont help alot lol! But i think your best bet is to buy a book! Sometimes is great to get a advice from the internet but nothing beats a book!

[Speedy88]

Yo homies. Wheels are now in motion and the plan is set.

I bought this from Theo. There goes all my savings!


Many thanks for that dude The plan is:

December 21st, insurance policy ends with Adrian Fail. 740 goes into the unit and I take out the pug to run on a new policy for cheap mpg winnings.

The money I save will be spent modifying the 740 properly. The list of things to do are:

Lower.
Source some bang tidy wheels (Might have already found some)
Fit 3" zorst for the spools.
Fit adjustable pressure kit on turbo.
Welded diff (for the why?! Because I'm actually going to give this drifting thing a go, properly).
Fix speedo.
Pay for an LPG conversion so that it's all efficient and stuff.

All this should be done around Jan or Feb. In the spring I'm going to paint it as the current body is pretty battered. Thinking matt blue or beige. Depends on which wheels I end up getting.

As for the 205? Might just source some nice wheels but nothing much, want to keep it standard and cheap.

[foggyjames]

Thoughts...

Don't weld the diff. There are actual (and damn cheap!) LSD options for 740s. It's rude not to.
LPG...tread carefully...very carefully! I'd almost be tempted not to, if you can afford to run both cars and won't be doing many miles in the 7. That thing should return 30-35mpg on the motorway, which isn't too shabby. LPG is a can of worms (although perfectly possible to do correctly) and perhaps a complication you don't need?

Also...if you want to show me this mis-information regarding turbos, I'll attempt to shoot it down...or concur and change my thinking. Probably mainly the former To be fair, the best option is probably to find a car which does what you want, and copy its setup.

cheers

James

[Speedy88]

LSDs are fine but I'm on a budget here, I haven't found any for less than £400. A modified locker is an option if I can find one and I do believe a welded diff done properly (IE, plated not just filled with weld) are perfectly reliable.

Interesting on your opinions on LPG, I've found those opinions across the board. However speaking to specialists, friends and Steve off VOC, I've also found those opinions tend to follow DIY jobs and the such. Steve's car was done by Dai's lot, he told them he wanted to do some turbo modifications and they fit a larger bias valve? I think it was? Basically it was already set up to allow tuning. The thing works flawlessly and as it was a sport he was already at 190hp.

If I get it done through a company, there's always men I can go back and shout at until it works properly.

[theo2468]

An I returned with this.

[foggyjames]

Nice work Theo!

As for the LSD cost... http://www.summitracing.com/parts/DTL-912A588/
...currently about £300. I really think it's rude not to If the budget is that tight, find yourself a G80 / 1041 back end, and chop off the weight. That works perfectly well, to be fair. In terms of welding...it's not so much reliability as the PITA factor...tyre wear, noise, difficulty parking, etc. I know it's not *that* bad...but still a PITA, and to be avoided wherever there's a reasonable-cost option. The 1041 is the way forward. Any 940 "Turbo" (i.e. an FT engine) should have one, although one from a 2.3 is advisable, as the 2.0s have a shorter axle ratio. Are you sure yours doesn't have one...?

cheers

James

[Nimminz]

Get any welding it needs doing done before LPG-ing it. Welding and can's of pressurised explosive gasses don't mix, thus why most garages won't weld on a car with an LPG tank

Plans sound good though

[SteveP]

The 1041 axle in my 940 was hilarious.... it locked hard on tight corners and hard launches. Ok so it's supposed to only engage at below 30mph or something, but to be honest where in the real world can you be going any faster sideways (anyway, it'll certainly help having the locker already initiate a slide). Beside's... the B200FT at 10psi and Nankangs on the back it'd spin the rears up in 2nd at 50mph at full boost in the wet

Personally I'd just fit one of these (if it hasn't got one already) and be done with it If you pick the right place it'll be dirt cheap too and you can modify it to lock at all speeds if required.