Outer Limits 4x4 Board

Ive just finished turboing a serria 1.3l. Im running throttle body injection with a blow threw set up. It is intercooled and running around 12-13psi. It Starts to spool at about 2200 and pulls hard till 3 grand but then it breaks down. I thought it was running out fuel so I thew a ajustable regulater on it and wound it up to 60psi. but it is still not reving out Someone suggested I could be snuffing my spark with too much boost could this be so?

Most likely blowing out spark or blowing valves open.
Joel

12-13psi This motor won't last through you ironing out the bugs.

Drop the boost to 5-6psi, knock some timing out of it, put 98 in it and drive it, very very slowly to someone with a dyno and get the timing and air/fuel sorted out.

It still could be running out of fuel - but seriously.... it could be pretty much anything. you are asking soooo much more of this motor than it was ever designed for- strewth, they ping dead stock when you get them hot

Have you done anything to drop the compression for this much boost? how much timing have you pulled out?

Steve.

That is of course correct, I'd assumed you'd tune a car that you'd just turboed??

Joel

Im running stock keverything. I understand the motor won't last long. As I will build it to take the turbo when it is shagged. I canot drop the boost as that is what the wastgate is set for.Im running 10dbtc What should I drop it back too?

Hey rhett, if youre wastegate has a threaded rod which holds the clevis on the end, then screw the clevis out as far as you can while keeping a few threads left, or even see if you can use joiners. Making rod longer will cause the wastegate valve to start opening much earlier, reducing boost pressure.

You will need to pull large amounts of timing out under boost due to the increased cylinder pressure causing much more rapid combustion (10 degrees or more), detonation will occur and the pistons will get holes in them. Doing this by retarding the distributor if it has one will make the vehicle sluggish down low. There will also likely be insufficient fuel for that level of boost, it will be maxing out its air mass meter and/or MAP sensor making the computer unable to cope at that level of boost.
You need something tuneable, bigger injectors as they wont be able to supply enough fuel, you could try a rising rate pressure regulator starting with with a 4:1 ratio and going up as required to get appropriate mixtures bearing in mind most stock injectors shut down at 70 psi fuel pressure. That will likely require a better fuel pump as it will raise fuel pressure 4 pound to every 1 pound of boost, you may need a higher ratio also.
Bassically, unfortunatly without tuneable EFI its going to be far from right even with all the patch ups.
Sorry Joel

Well put.

Sierra motors were never intended for boost. because a turbo can be bolted to the side of a motor doesn't mean it is a good idea. I would suggest that TBI and the stock ignition system are both unable to do the job in a boosted application where accurate control of fuel and timing are required under a large range of operating conditions.

Perhaps as a starting point, a 16V vitara MPI head and injection gear would be a wise investment, and an aftermarket computer.

Steve.

Here's a link that is about a 1.6 8v Vitara with TBI and a turbo. http://wildcatent.freeyellow.com/zookmods/ It will give you a little insight as to the fuel v boost requirements you need. Do a search on the Zukiworld forum for posts by Wildgoody and turbo for more info. The 1.6 16v setup seems to be good for 5-7psi max in stock form as the MAF and the ECM seem to be able to cope to that level. After that you will need more mods like an aftermarket computer and injectors, etc. to keep it working properly.

Ok Im back on this topic. I went out and built a motor for this car with suzisport lowcompression pistons moly rings gti rods ect. I am still having trouble, I still have my rockcrawling zook running the same computer same turbo same throttle body and stock motor and it still hammers all the way to redline. I have swapped the injectors swapped the computer and taken off the intercooler but still breaking down. I have wound the fuel pressure up to 60psi and all it does is fuel up the plugs at idle. ANd yes Im taking it to the dyno he just couldn't fit me in this week.

you can buy a bleeder valve from any auto shop to adjust your boost down to 6-8 or what ever you want

Rhett , did you use the GTI crank and grind down the mains to suit the sierra main bearings. Did you have to shorten the piston or are the new pistons shorter being a lower compression piston. I have got my engine going running no more than 6 PSI , it seems to run okay at the moment but I to am yet to tune it on the dyno , I would be interested to see how you go , I have fitted an adjustable blow off valve and according to the boost gauge lets go at 6 Pound , I just need to plumb it back to the air filter to keep the crap out of it , Cheers Paul.

I used a serria crank as I havent broken one yet I used those 16 valve turbo pistons that suzi sport sells and gti rods to get the 19mm gudgen pin to take the turbo pistons. the compresion hieght was about 1.2 mm lower than the serria piston and rod but I figgured if it was too low in comp. I could take a bit off the head at a later date. I have no doubt this motor can take 20psi comfortably I just got to either get the fuel into it or spark it some how. It just makes it hard without puting it on the dyno.

Rhett,
Whats the coil output at the spark plugs, it sounds like its looseing spark under boost... What plug gaps are you running??

Do you know how to test for coil output??

I don't know howq to test coil output can I do it with a multimetre? Its running a coil pack in the dizzy does that make it harder to test.

When working on the motor and its running I reckon I get lite tingles every now and then, could this be an earth related question?

Cut the wastegate rod and put in an adjustable threaded section. Then you can wind the boost up or down as needed.
I imagine you could drive a stock motor on maybe 4psi boost without problems, but not 13.

Ive near given up on this motor. I have swapped just about everything from the idential setup that works well and it is still playing up. I have taken the airflow senser, the injector, dizzy computer, even the hole loom out of the other car and it still won't run past 3 grand at full throttle. looks Like I got to put the turbo built bottom end in the otherzook and build a high compresion bottom end for this one.

What do you mean when you say it won't run past 3 grand , does it break down or does it hunt , where you hold it at 3 grand , what does it do exactly , Cheers Paul.

It will go past 3 grand at half throttle and it will go past 3 grand at full throttle n/a it is going into some sort of limp mode at about 3 grand at full boost and throttle but I can;t work out why when it dosn't on a identical setup.

heres a stab in the dark.

Are you running a snorkel?

Is is a plastic one with plastic air pipe ?

If so, disconnect it and run the air cleaner only. See if that helps.

( Recent experience with a 4.2TD GU, would not rev past 3 grand, turned out to be the snorkel constricting airflow, imploding, disconnected, and presto problem resolved. Now going stainless all the way)

So when it goes into limp mode does it rev up and down when you hold the acceleratorat 3 grand. Mine did something similiar , does it idle okay or is it reving a little high , mine was a dud ISC solenoid not operating and if this does not let the right ammount of air into the TBI it will hunt , I to changed everything and it was was the one part I didn"t replace , Cheers Paul.

Edit , if you have changed the hose on ISC this can also make it hunt.

It Idles perfect. The ISC is where the water comes threw the throttle body yes?

What TBI you got , CHeers Paul.

mazda 121 bubble

Do you have a diagram and does it mention a ISC solenoid or something similiar , There should be a 1/4 or 5/16 hose of the TBI , at the base and this controls the air into the ISC , has an electric solenoid which varies air flow , Cheers Paul.

All I know is there is two places water enters the throttle body. One has somethng to do with running cold and the other I wound't have the fogest what it does. I have probly restriced the flow in my adaptor plate a little could this be it?

Pretty sure I asked you before but do you have the diagnostic plug still in the loom?

sounds to me like it knows its not keeping up and cracking the sads, have you swapped the whole throttle body and TPS over?

Water just gets pumped through TBI , to heat it up , What sensors or solenoids are hanging of the TBI , got any pics and as you say is the adapter plate and manifold the same and is there any air inlets on TBI and what size are they , Cheers Paul.

Rhett wrote:It will go past 3 grand at half throttle and it will go past 3 grand at full throttle n/a it is going into some sort of limp mode at about 3 grand at full boost and throttle but I can;t work out why when it dosn't on a identical setup.

Wat sort of boost is it running when it breaks down? Can you adjust this at all?? Are you running the standard bubble MAP sensor? Have you tried replacing it, could be damaged or giving you funky readings.

Cheers Dan

Swaping the whole heads, intake manifolds and throttle bodys between the two cars this weekend Will see how it goes then