|
|
Post by Dog on Dec 8, 2007 19:47:24 GMT 1
Hey all. I've noticed that some people want to know how to power tune a 998. Other than doing your norm of fitting a stage 1 kit, and a good rolling road session, I am going go beyond that. This is going to be a project-ish type thread, so as I work on the engine, I'll update it here, and try and make a "blow by blow, how to" thread. My aims for this engine is a full strip, and start from a fresh block. I am not reboring this 998, but, if you intend to rebore, the rebuild process is the same, your just using different size pistons. The hopeful spec of my pokey 998 will be; 12G940 head (1275 head) I'm personally going to be using one off a MG Metro, as these heads were ported, and had bigger valves as standard. A higher compartion ratio, currently I know the engine I am using has around 8.5:1CR, I hope to rasie this to around 10:1. A 1275 camshaft, I am trying to get my mitt on a MG Metro cam, as these are a modified version of the normal 1275 cam, so its ever-so slighty "hotter". I'm also going to use a GT gearbox that I've had lay about for a while - just to get it out of the way. This will then have the standard running bits, dizzy, single HIF38 carb, LCB, 1.3/4 exhaust system. This, if built properly, should give around 50-60bhp and float around the same figures in torque too. Its nothing racey, just something slighty more pokey for a person that likes to take "long-cuts" home from work  I'll add pics as I progress, but as this is the start, is there anything anyone wants me to go over in detail at all? Cheers. |
|
|
|
Post by dai9fxey on Dec 8, 2007 19:55:21 GMT 1
 Nice subject to cover Dog. What with the shortage of 1275 lumps and the increased insurance costs the 998 motor is an ideal choice. Will you be using the standard flywheel etc.?? Will you be using the 1 1/2 or 1 3/4 carb. 
|
|
|
|
Post by Dog on Dec 8, 2007 20:19:55 GMT 1
Nice subject to cover Dog. What with the shortage of 1275 lumps and the increased insurance costs the 998 motor is an ideal choice. Will you be using the standard flywheel etc.?? Will you be using the 1 1/2 or 1 3/4 carb. With insurance, be careful, although you are using a 998, a "tuned" 998 can sometimes be more costly on insurance than a standard 1275. So before opening the tool box, please check the insurance. But as you say Dai, the shortage of 1275 engines is actually now starting to hit home. More and more people are now starting to go back to tuning the small bore enignes. For me, I am only building it as a "just in case" engine, as now, I have two Minis to run  Anyways, to answer your questions. Flywheel, I'll be using a 1275 Turbo flywheel, or you can run anything you like in all honesty. Depends if your running a pre-verto or verto clutch. I will be using it as a standard weight, due to using a longer duration cam, the weight will help it tick over better in traffic, but not let it spin up extreamly fast. Horses for corses on that. I'd advise not to get "Ultralight" flywheels for a hot cam'd 998, as there just isn't going to be enough torque to keep it smooth in traffic. Unless you like the feel of a lumpy engine, then go for a ultralight, but a steel billit "lightened" flywheel will be fine. The steel flywheels tend to be around 11lb in weight, which is perfect for a daily motor, where the driver would like a bit more pep As for choosing the clutch, like I said, depends what you like. On the 1380, I've used a pre-verto, as the pre-verto can cope with more power, than the verto, but if you've never used a pre-verto with a uprated clutch plate, its best to discribe it as on or off... you can slip it, but not unless you have strong legs. Whereas the verto clutch, is designed to be slipped (mainly found in A+ engines) but the draw back is, your limited on how light you can go, and what clutch plate you can have. The main two plates for verto clutchs are standard, or turbo. The turbo is in my opinion the better one to go for no matter what state of tune an engine is in, it'll cope with up to 95bhp-ish before it starts giving jip, so perfect really for a powerful small bore engine. Induction, theres nothing to warrent a 1.3/4, its far to big for a small bore engine, no matter what anyone says. Stick with either a HIF38/HS4 or twin HS2's. I'll personally be using a HIF38, but going to try and do the Vizard treatment to it, and see if that actually helps with power/torque. Oh and another thing before I go and forget it, you'll need a 1275 Head gasket, I'll recommend the Payne BK450 - one of the best "standard" gaskets on the market, they will cope with 11:1CR 1380's up to around 60k miles, so perfectly good enough for the 998. Although they will go straight on, they do require some slight tweaking, as some of the oil/water ways don't quite line up. I will show you where and what to do when I get that far  |
|
|
|
Post by Specialbuoy on Jan 7, 2008 0:57:33 GMT 1
Dog, When will I become a fountain of knowlegde like you?
|
|
|
|
Post by Dog on Jan 7, 2008 21:31:44 GMT 1
One day, young Jedi!
|
|
ljonez
turbo
Built not bought
Posts: 3,734
|
Post by ljonez on Feb 20, 2008 1:31:10 GMT 1
i just finished building a very simular spec engine, mine is
1030 block (998cc +40')
rebuilt 12g940 cylinder head
sw5-07 cam
lightened duplex gears
stage 1 kit
center main strap
rebuilt box
megajolt
stage 1 kit
hif44
its bhp is estamated at around 60bhp but itwill be going on the rollers soon to find out for sure. in its current un-setup state its bloody fast and revvs very very freely.
good luck with your build and write up, any questions feel free to ask
|
|
|
|
Post by dai9fxey on Feb 20, 2008 9:16:23 GMT 1
I like the sound of that. Be interesting to see the results of the Rolling Road session. Keep us posted.
|
|
|
|
Post by thereddwarf on Feb 20, 2008 12:10:17 GMT 1
where are you taking it for the rolling road...thinking about getting mine sorted very soon
|
|
ljonez
turbo
Built not bought
Posts: 3,734
|
Post by ljonez on Feb 20, 2008 18:38:38 GMT 1
not sure yet, as i have to find a place that can map megajolt. apparently there is one in abercynon but i heard he has closed down
|
|
|
|
Post by byron101 on Feb 20, 2008 18:57:44 GMT 1
the 1 in abercynon who supposed to be good is behind the lpg gas place by the lights, don't know if he still there though
|
|
|
|
Post by Dog on Feb 20, 2008 19:35:42 GMT 1
Scrap the HIF44 - its too big!!
a HIF38 will be perfect for the cam too!
|
|
ljonez
turbo
Built not bought
Posts: 3,734
|
Post by ljonez on Feb 20, 2008 23:14:00 GMT 1
Scrap the HIF44 - its too big!! a HIF38 will be perfect for the cam too! i initaly run it on a hif38 and it performance was okish , switched to the hif44 running a bdl needle and its made a big diffrence definitly wont be going back down to 1/2 inch carb now. |
|
|
|
Post by dai9fxey on Feb 20, 2008 23:20:47 GMT 1
Was there a big difference in the MPG when you swapped the carbs. |
|
ljonez
turbo
Built not bought
Posts: 3,734
|
Post by ljonez on Feb 20, 2008 23:36:56 GMT 1
Was there a big difference in the MPG when you swapped the carbs. nope stayed around the 45mpg mark on a run posibly a bit more but most of my driving is around town at the moment and i havent checked that yet |
|
|
|
Post by dai9fxey on Feb 20, 2008 23:44:08 GMT 1
All those extra gee gees and the MPG's about the same as a standard 998.
|
|
|
|
Post by Dog on Feb 21, 2008 0:27:53 GMT 1
I think you'll find you've lost torque and reaspose with the HIF44 - but if u say its better its better, I am not going to argue...
Even though my 1380 is running a HIF44 and a BDL... makes u wonder...
|
|
ljonez
turbo
Built not bought
Posts: 3,734
|
Post by ljonez on Feb 21, 2008 1:06:07 GMT 1
Even though my 1380 is running a HIF44 and a BDL... makes u wonder... isnt the BDL the recomended stage 1 1275 needle? |
|
|
|
Post by Dog on Feb 21, 2008 19:02:12 GMT 1
Tis that.
But the HIF44 can power a motor of up to 90bhp.
With my 1380 - its been built with nothing but torque in mind...
I won;t go over the spec, as this is about small bore tuning...
|
|
ljonez
turbo
Built not bought
Posts: 3,734
|
Post by ljonez on Mar 12, 2008 19:18:10 GMT 1
just sorting out some pics and found this from my build.  thought it might help to give people an idea of how the pockets look. the ones in the pic are 1cc in size |
|
|
|
Post by Dog on Mar 12, 2008 22:43:57 GMT 1
What comp ratio you working with?
|
|
Nice subject to cover Dog.
