Turbo Xflow ... worth it?

[bytesandbolts]

Onyd, I understand and appreciate both of yours and Grahams comments, thanks again guys. From looking at my map I believe i'm running 34degrees max advance, I'll try and dig a little deeper to confirm that as I'm not too familiar with the software still. I've attached a screenshot of my MS3 dashboard, to clarify it's running the map I ran on my car, but its using the JimStim simulator to simulate tach input/sensor input etc, so some values might be off.

Thanks for the tip, I'll give the DynoPerformance a ping and see whats that.

[Dyno]

34° sound a lot to me but I believe this is the value with no boost. Use something to put pressure on your map sensor and go to the boost level you where running. Bring RPM back down to 3000 RPM.

34° is still a high level without boost. Don't think you will need much more as 30° (even less) with no boost.

[bytesandbolts]

Yes I believe you are correct about that, I did consider this earlier and have been reading to find the value in the software settings.

[Dyno]

You can take a screen shot again (with right boost pressure simulated) or post the ignition setting table. If you don't have other big offsets programmed like silly retard in function of temp etc.. the value for ignition is as set in the ignition table.

[Rob Williams]

Hey does anyone mind if I resurrect this zombie thread? Reason being that my discussion is based on what I've read here and I figured the conversation wont repeat itself as much this way.....
Anyway, YES I'm going to build a turbo'd Kent 1600. It's not for outright HP figures but more to have something with a bit more ZIP that standard, and because....well....why not. Looking at builting to cope with max 10psi, but probably only run 6-8psi in reality.
What I have gleaned so far from this discussion is to use a 711M block rebuilt with 681F(?) (chambered) head to get 8:1 compression, OR use forged/coated LC pistons (if I could GET such a thing?) to bring down compression to 8:1, or in conjunction would be 7:1 (?).

My local carby builder suggested that blow through will be better for my application due to stuff we didn't get a chance to talk about. He suggested a rebuilt Weber 38 DGAS converted for the purpose. Also said they build hats when I know what cross-over pipe diameter I'll be using. He said that the renault 5 carby would be an option, but not the best one.

Apparently blow through also don't require/need an intercooler and freezing is in fact more of an issue.

For turbos both T15 and T25 have been suggested. I'd like boost to come on low as it will be a driver and hopefully wont see redline often. I think if the boost was maxed out by 5K that would be fine by me.

I'm thinking about building the setup onto the existing original motor and running it low-boost while I build up a dedicated 711m based motor. A couple of PSI should be ok on standard motor in good nick?
What recommendations for the material and size of cross-over pipe?
Should I upgrade the fuel lines/fuel pump and if so, what size?
What type of plugs should I run?
What else am I missing?

[Graham]

Ren 5 carb wouid be a FAR better option than a 38dgas, they are talking rubbish about intercoolers too, unless you are running VERY low boost its better to have one

[Rob Williams]

Why would the ren5 be better? He did say that the weber would be purpose built.
...and why is it rubbish about intercoolers on blowthrough set-ups? Am I getting confused (very possible lol) and it's draw through that has the possible freezing problems? I'm new to forced induction so I'm trying to learn as much as possible. Boost will be <10psi. Is that considered low?

[Graham]

because the ren 5 carb is designed for forced induction in the first place, secondly the 38 dgas is way bigger than needed, its not a good choice for an N/a x/flow let alone a boosted one.

suck through installations would have issues with a wet mixture having to travel so far to reach the engine, blow though its air only and the fuel is added one the air gets to the engine. and yes such through you are more likely to encounter carb icing.

merely compressing air makes it hot, put your hand on a working air compressor and your realise just how much heat it makes, hot air is bad for the engine because not only will it encourage detonation, but the fact its hot means its not very dense, so your loosing 50% of the benefit of compressing it in the first place, so an intercooler is best unless as i say you have very low boost, modern cars all have intercoolers even ones with tiny tiny turbos and little boost, they wouldnt fit them unless there was a reason

[Rob Williams]

Cool - thanks for your advice, I'll continue researching.

[Dyno]

If you are looking for an 'unfinished project" go ahead with the 38DGAS. Believe me, it's the last carb you need. R5 turbo is probably the best option. followed by my favorite DMTL but if your carbs skills are very low, please use the R5 carb.


It is indeed so, with carb setup the air will go into the engine a lot cooler as with fuel injection and does make the need for an intercooler less urgent from a "power point of view". But I do suggest you use an intercooler for anything higher as 300 - 400 mbar. This will help the engine staying cooler and is also important.

[Mark V8]

What about a Lotus Esprit turbo carb ?

Designed for blow though and a single one could be used on suitable inlet manifold

http://www.lotusbits.com/esprit_engine.html

[Dyno]

Yes, Esprit Dellorto's where turbo carbs but please beware, they have no real boost sensing device as the R5 carb. The extra fuel at the right moment (an no fuel if you did not needed) came from a very complex setup with booster rings, over pressure at the float chamber, selected emulsion tubes, Try-jet at high velocity etc.... All the kind of "trick" you can read in tuning books about making carbs work for turbo.

What I discovered, even if it is working for this Lotus, it's far from sure it will do anything for your KENT turbo. When I wanted my own turbo carb I've test and played for days with these trick of booster rings and all I've named and ever read about. None solved my problem over the whole line. It was way to complex and you could not duplicate anything to an other engine. What is working for X was doing nothing for engine Y. You could not call it a "universal" turbo carb as I wanted. Reason I stopped, did small mods to the carb and the rest of the fuel as I explained before. Valves and hobbit pressure switch connected from float chamber to the carburetor choke.

So without a good knowledge of carburetors or a good box of beginners luck beware if you start with this Dellorto.

[Rob Williams]

Interesting stuff. One problem is here in Australia the availability of R5 carbs is scarce to say the least. Lotus stuff? Forget it. I appreciate the advice but can someone elaborate as to WHY the DGAS is no good and WHY the R5 is better? The carb guy I was talking to here in Aus basically said that any factory turbo cab would be the smallest required as they were just trying to get a small motor to a base level of performance. He said that the 38DGAS would let more air through allowing the motor to breathe better, in turn allowing the turbo to spool up more readily. Is this snake oil? I would have thought that bigger was better, and that weber was better than solex? What is it that the solex has, that the weber doesn't? I want to use a single down-draught carb, so again the lotus set-up or similar is a no-go for me.

[Graham]

is there really any point in repeating the R5 carb is made for turbo charging? even ignoring that fact that the dgas isnt designed to work under boost bigger isnt always better, a big carb will need masses of air through it to draw fuel through the mains, if you were fitting it to a 4 litre engine or an engine with a huge turbo which reved to 9,000 rpm i might agree you want a big carb, but the fact is you dont.


Ondy has his own dyno and has done a ton of testing, he even makes his own carbs, if he says the carb wont be any good its a pretty fair bet it isnt, he isnt a bloke playing in a shed at home, check out his gallery
http://www.amtdyno.be/index.php/gallerij

[Rob Williams]

Ok I trust ya, was just trying to learn more about the carbs. Seeing as these are rare as hens teeth here are there any other options?

[Dyno]

If you would fit the 38DGAS on a KENT it would already be one big disaster. Let alone with a turbo. It's even to big for most road going NA Pinto's. It's also not progressive (both throttle plate open at the same time) and not a good idea for any turbo engine because you have less jets to play with.

If you go blow through the carb size does not have to be any bigger as it would be in NA case. Can even be taken smaller. The air is denser, no higher speed. Suck through is an other story, here the carb should be bigger but still progressive would be a lot better. For such through, try SU HS6 or HD8 for a very big engine. HS6 is OK for most engines. You need a turbo with seal or take out the throttle plate from the SU and fit a throttle body after the turbo.

Possible your dyno man has used 38DGAS with success in the past but will all have been big 6 cylinders, not KENT 1600 cc.

Try Ebay and buy one in Europe. Postman will deliver to Australia. It has nothing to do Weber is better as Solex. Renault has forced Solex to build a real turbo carb and they did it right. Renault where masters in turbo charging engines with carbs where all others failed.

[Rob Williams]

Thanks Onyd - I was wondering why he suggested a synchronised carb and not progressive but I figured it was a turbo thing. There's a place here in australia doing blow through kits for kents and izusu motors and they seem to also use weber exclusively....but that's probably a supply thing. I'm guessing the Solex 32DIS is not available new.....?

[Rob Williams]

Thoughts on this?
http://www.ebay.co.uk/itm/2220075414...MakeTrack=true
Anyone speak Italian?
http://www.ebay.co.uk/itm/CARBURATOR...kAAOSwu4BVkssJ
Or this? http://www.ebay.co.uk/itm/Renault-5-...IAAOSw3YNXZt9~
Still figuring out what I'm looking at

[Dyno]

I've never said you can not use a 38DGAS as turbo carb but will take a lot of work and best 6 cylinder engine to start from. But you need a lot of reworking, rejetting and it seals very badly. There is a lot better on the market. Maybe he is building suck through. Plus, beware for "turbo kit's". Many are never tested or tuned. You only receive parts.

Only the last link is the real turbo carb. I've you are sure about the project I would buy and rebuild this R5 carb and find a single carb manifold for the KENT. The other cabs are no turbo. Not all Solex 32 are turbo carbs. If comment is right it has the large bore group 5 body (large choke).

From time to time I see them showing up new on ebay but is always NOS. I've sold my last new one a few years ago and all gone now.

[Rob Williams]

Okay thanks Onyd. I know nothing about solex carbs so learning curve is steep (only really played with Hollies). I do have a single draught manifold here already If you see one and think of it, pls let me know. I'll go back to that last add and read further. There's NO sign of any local to me but I'll keep scouting the renault wreckers in case.
Cheers,
Rob.

[Rob Williams]

Disregard, I've just gone out on a limb and bought that last one. Will keep anyone interested updated on (slow) progress.

[Dyno]

take it in bit's and pieces, clean it and fit a rebuild set (gaskets etc). 80% of you turbo setup is done already !!!!! Good luck with the other 20% but sure you will make it with this carb.

[Rob Williams]

Old-mate who's selling it says it's been recently rebuilt but might have to be jetted down to be a bit more polite. It's got to travel halfway around the world but the price is comparable to a rebuilt weber here. I'm glad I've been able to act on your advice - and that I was lucky enough to get what was recommended. Next on the list is the turbo/manifold.
I have a mate who's keen on selling me his brand new generic T28 for the car.... I've been told by others to get a T25, or even a T15. Online Turbo calculators suggests a T25. What's the difference?

[Dyno]

Problem with turbo's is that there as many sizes in these T25 and T28. From very small to very big. Most easy is to buy a turbo from an existing car with approx the same power as you are after. The smallest size SAAB would probably be OK, one of those 2 Skyline turbo's? A good old T3 from and Escort RS turbo can be used. Bit lazy compared to newer ball bearing turbo's but can.

[Rob Williams]

Righto - thanks for the tip

[Rob Williams]

Ok so while I wait for my carby to arrive, my head to arrive, and generally mooching around with bodywork I'd like to ask some more advice pls. What do I do about the PCV on a boosted engine? Obviously there will be boost not vacuum in the intake so it can't be plumbed there. It has to be plumbed somewhere to pass inspection though....what do I do?

[Rob Williams]

So I'm trying to learn more about turbos. My research indicates that in the garret range I should be looking at a GT1548 - upto 1.7L, 100-200hp. Next bigger option is the GT2252, but it says it's more 1.7L-2.L at 150-260hp. Remembering this is for a DAILY drive on a kent engine I'm seriously thinking the GT1548 would be the one to go with for drive-able boost 2K rpm-4.5K rpm. Thoughts?

[MegatronUK]

Ok so while I wait for my carby to arrive, my head to arrive, and generally mooching around with bodywork I'd like to ask some more advice pls. What do I do about the PCV on a boosted engine? Obviously there will be boost not vacuum in the intake so it can't be plumbed there. It has to be plumbed somewhere to pass inspection though....what do I do?

You need a one-way valve in the inlet manifold, so it can pull crankcase vapours at idle/vacuum, but not pressurise the crankcase when under boost. The Cossie has one of these in the plenum, and I'd guess most other turbocharged motors have something similar:

http://www.ebay.co.uk/itm/New-Plenum.../162108658276?


If you are running a servo you'll also want something similar in the vacuum line to that as well.

[Rob Williams]

Thanks. I had assumed that the crankcase would have to be ventilated at all times - especially as the revs increased - not just at idle.

[MegatronUK]

The other option, rather than feeding the vapours back in to the inlet is just to vent to atmosphere, or into a breathable catch tank. Remember that as soon as you come off the throttle the inlet will be making vacuum, rather that be under positive pressure. If it wasn't, then your servo wouldn't work

[bytesandbolts]

Remembering this is for a DAILY drive on a kent engine I'm seriously thinking the GT1548 would be the one to go with for drive-able boost 2K rpm-4.5K rpm. Thoughts?

My Xflow Turbo used a GT15, drove great as a daily. The setup runs fuel injection though.

[Rob Williams]

Cool - can I pick your brains a bit about it? So no dramas with temperatures from a small turbo? Did the turbo running out of puff up the top-end? What boost were you running on average and when did boost start coming on?

[bytesandbolts]

Sure - I had a small chunk of piston break off in one of the cylinders, as well as two pistons rings failing which obviously demanded a refresh of the engine. However once we had stripped down and examined all of the parts we realised that the engine was still OE Ford. In short the engine failed from wear and tear, but the added turbo definitely did nothing to help. When it was running I used it mostly in city traffic in London and had great drivability, it also covered a lot of motorway miles which again it coped with just fine, plenty of overtaking power in 5th. Running 7 PSI so low boost, boost came in around ~1500 RPM. It's definitely worth pursuing if you want power (but it doesn't come 'cheap') and unless your willing to really put in the time to create a good setup (ideally taking advantage of EFI) then your most likely reducing the overall reliability of the engine as your increasing it's complexity (added components, lots of extra heat, much higher pressures etc).

[Rob Williams]

Yes I agree. I'll be building a motor to suit the turbo but it will still be very basic. I'm trying to make the whole thing as basic as possible.
So far what I have in mind is:
Renault GT5 carby (my own reasons for not going efi) on standard ford intake.
711M motor with 681F (chambered) head with 3 angle valve job, HD springs, matchported to intake, polished chambers(?). Should drop it to 8:1CR?
Standard or GT cam (probably GT).
Double row timing chain.
Polished standard pistons (From what i've read forged wont be required...?)
Balanced rods/pistons/rotating assembly (is it worth deburring/polishing rods?)
High capacity oil pump,
Dizzy to suit. Possibly electric.
Plugs to suit.
Either GT2252 or GT1548 turbo.
Either straight pipe or small top-mount intercooler.

From what I've found out this set-up should be reliable with 7/8psi?


Boost coming on at 1500 sounds a little early to me....but I guess it would have no lag

[bytesandbolts]

I can't comment on the carb stuff as I've focused all my research solely on injection setups. Any particular reason why your using a chambered head, they are pretty poor from what I've heard, instead why not leave it at standard CR with a regular head. But that said perhaps its best to lean on a side of caution because the fuelling can't be controlled as accurately as EFI.
Most of the other stuff looks like good housekeeping, so why not if you wanna spend the cash and time.
Intercooler yes, all modern turbos run them so classics should too in my opinion.
The turbo is absolutely tiny, boost does come on quick. I wanted acceleration instead of speed.

[Rob Williams]

Yep, I'm using a chambered head as the standard 711M with the flat head is 9:1CR. Using the chambered head adds another 8cc(?) to the pot which brings down the CR to 8:1, which is more boost-friendly. What have you heard that is poor about them?

I'm using a carby for a few reasons - a) An inherent distrust on the reliability of anything depending on a computer b) Injected engines in old cars always seem to take away a bit of the charm/character c) minimal disturbance to the car itself and if I air condition the block on this one I can put the original motor back in more easily d) cost/time/brainpower.

[bytesandbolts]

If you use the regular pistons which have the combustion bowl in the crown with a chambered cylinder head, then that will reduce your CR but may affect the squish. So you might be helping one problem but potentially creating another. Those heads were designed to run with flat top pistons.

I don't know I'm no expert, it's just something to ponder over. Are you fabricating your own turbo manifold?

[Rob Williams]

It's only a very SLIGHT chamber - most of the combustion still takes place in the piston. I don't think they had flat-tops in the crossflow. I have a mate who is keen to fabricate a manifold but I'm leaning heavily towards just getting one from turboescort.com here in Aus.

[Graham]

crossflow never cam from teh factory with flat top pistons, although there are plenty who have fitted them with a fully chambered head

[bytesandbolts]

I thought the 681F was pre xflow - my mistake.