Flat Spot?

[tay]

Alright lads haven't posted in a while, hows everyone doing??

As you may or may not remember I was in the process of fitting a GTE engine on Twin 40's into me 1.4SR. Its all been done and tuned up by a carb specialist, but there is a flat spot they can't get rid of at about 2000 - 2500 rpm. They reckon that the standard cam on the injection engine does not have the overlap required for the carbs, so they have suggested that a new cam (Kent I think) designed especially for the twin 40's will do the trick. They've also suggested a Weber Alpha 3D ignition management thingy will greatly improve the performance of it as well.

Anyone know if any of this is true, or are they just trying to con me hard earned off me? Also what sort of power would i be looking at realisticaly?

Cheers lads

[Dicko]

for the cost a cam is well advised and cant belive you havent already got 1!!

as for the ignition, yes it does help but its also expensiove as far as i know.

entirely upto you

[MC]

Regarding the Flat spot, what chokes and jets are fitted? Without this info I can't help.

I assume that if you haven't forked out for a cam yet, you probably haven't had your head done either? If this is the case, I'd buy the cam (rally one is the only one worth going for, it's not lumpy and you won't loose driveability with a 1600 on carbs) and get a DECENT head. Power gains from this will make anything you get from a Weber alpha management look silly. I'd only do the mangement when everything else is 100% tuned and you are trying to scrape in the last few horses.

MC

[tay]

after all this time i've now done the right thing and got the Piper cam fitted (the one specially for Twin 40's) and the Alpha 3-D management but wait for it ............... ITS STILL GOT THE BLOODY FLAT SPOT :x :evil: :x !!!

To top it all off when it was rolling roaded and all fitted the bloke said the 'Power was really good', but when i got the print out it showed a peak power of 93bhp at the flywheelI thought a standard GTE had 100 !! ! So to cut a long story short IM PISSED OFF !

anyone got any suggestions why the crap power (Its a reconditioned 1600 GTE with piper fast road/rally cam, Twin K&N's, Powerflow full exhaust system and Weber Alpha 3-D igntion management) ?

Cheers

Tay

[Dicko]

did they check the timing of the cam belt?

I had a really underpowered GTe engine, advanced the timing by 1 tooth and it was a completely different animal. no pull at all below 4k rpm and not much better above.

a mate of mine has an sri and its completely lost all power recently, put out 95bhp@wheels last year, then died overnight, done a compression test of its low on all 4, but we cant figure out why. Do a compression test and check the timing.
What i did was to take the outer cam cover off, take out plug 1 (next to cam belt) and stick a long wooden cane down the whole, keep moving the wheel round with the car in gear until the stick gets to its highest point (top dead centre). the marks shud line up perfectly from this point.

[tay]

ill give it a try - cheers mate

[tay]

i know this probably sounds like a silly question - but how do i do a compression test ?

[Dicko]

take spark plugs out, and use a compression tester, make sure no fuel it geting in and and coil is disconected before hand.

i think halfords sell these, or take it to a garage should charge about ?10

[CP]

Doing a compression test is a good idea. Its the best way to tell how worn your engine is. Do it to a warm engine. Should be over 100psi as a guide? Squirt a little oil in down the plug hole and re-test. You should get a higher reading which will allow you to work out he precentage loss down the bores. If you don't get a change in readings and the compression is low then it probably means that the valve seats/valves are damaged.

However it maybe that this isn't whats causing the problem.
I did a similar conversion and had a similar disappointing result.
I fixed in 2 ways:
1. I got the head sorted with a big valve conversion and flowed throughout ( Blydenstein B++) This in 1 stroke will unlock maybe 50 hp with your other mods - you should be in the region of 140 - 150hp at the fly
2. I used another rolling road that knew what they doing. They all vary in their readings. Most read high - some however read very low. I would take any power readings or anything that these guys tell you with a pinch of salt. There are a lot of them that don't know what they are doing with 40's

other points:
what chokes and jets are you using?
what exhaust do you have.

[Anonymous]

should be over 100psi as a guide

More like double that on a healthy 10:1 or so compression engien, unless you have a cam with loads of overlap which will lower the figure a lot by allowing the air to leak.

Chip

[d0gz_bollox]

my 1.6/1.4SRi thing had 250psi in each cylinder (max on scale). it subsuquently blew up. 1.4SRi heads and 1680cc blocks dont go well :(

[tay]

I've just tried to copy in the rolling road graph but its not copying in for sum reason. Here are the figures anyway - I'm gonna have a look at the jets in a while and post them on here as well. These are the readings on the print out -

RPM Wheel BHP Flywheel BHP Torque
3000 57 71 125
3250 58 72 116
3500 62 78 117
3750 67 83 116
4000 68 86 111
4250 68 85 105
4500 69 86 100
4750 66 83 91
5000 67 83 87
5250 61 76 76


This is for a reconditioned 1.6 GTE engine with Piper Cam, Twin 40 DCOE's, POwerflow exhaust, K&N air filters, Alpha ignition management (no distributor) & Splitfire Triple platinum plugs !

Im gonna get a compression testing kit next weekend - but if it is low like you mentioned, how do i sort this out ? Im gonna get the Blydenstein head done as well so will this help on the compression side ?

Cheers lads !