is CT26A too big for a 1.8L?

[CHB]

i have doubts about my engine combo recently. i have a turbo 3TC, i'm using very low comp forged pistons for the engine internals and using a CT26A turbo off a 7MGTE.
recently got it tuned and revv cut has set to 6500RPM in the Megasquirt.
the power is only so-so, not much pull if compare to my mate's 4AGTE. he has a custom garrett turbo. he didn't use programmable ECU but using the late model MAP 4AGE NA ECU and his combo only boosting 0.8Bar.. i've sat in his car and the power level is so much different than what i have from a 1.8L with programmable EFI.
where did i missed out?

[o_man_ra23]

A couple of things... first is how low is the compression?? This could be a big factor, and your mate with his 4A could be running much higher compression, which will give better off boost torque, and faster spool.

Second, did you have the turbo tested before installation?? It could be a dud turbo.
Third, how good is your tune?? Especially spark curve. Was it done professionally, is it something your personally capable of doing (using a wide band oxy sensor of course), or did you go for near enough is good enough??
Fourth, its a turbo designed for a 2Ltr, so it will be a touch laggy, did you balance the motor when you built it?? In which case you should be able to open up the top end, which is where it will work.

There are soooo many variables, you need to document exactly how the motor was built, and even some screen dumps of the ECU maps would be nice.

[Norbie]

Fourth, its a turbo designed for a 2Ltr, so it will be a touch laggy,

Actually it's designed for a 3L engine so it will be stupidly laggy. Methinks the turbo is just too large to perform well on this engine.

[Kedderz]

agreed the 7mgte ct26 is just way toooooo big for a 1.8 litre.

[The Real Roadrunner]

should be possible to swap the rear housing over to an mr2 unit (may need slight profiling internally to suit) then swap rear flanges and lag would decrease somewhat but remember its a 20yr old turbo so performance will never be good compared to a garrett.

tuning can have a large affect and so will cam timing so some dyno time would be a good thing.

cheers
linden

[TE72_1800T]

i have one on my 3TGTE its not that laggy it gives u a good kick in the pants at about 3500 revs and is definatly a good upgrade from a CT20 and can hold full boost until like 7000rpm (thats all i rev 2). apparently mine is off a landcruiser not sure of the specs compared to one of a 3s or 7m but yeah. and like roadrunner said its a 20yo toyota turbo, i wouldnt have expected it to be anything like your mates custom garret on a 4age. how much boost are you running?

[o_man_ra23]

Ahh... I didnt realise the 7M ran a single CT26... that makes a lot of difference. Sell it and buy a CT26 from an MR2 or Celica GT4, that will be an instant improvement. Or you can get turbos for around $800 new about that size (Otomoto sell the KKR brand, and there is anothe one new on the market advertised in Fast Fours) which should be an improvement on the 20 year old item your toying with.

[CHB]

i never test my static compression ratio during my engine rebuilding, but the piston is dead flat with the deck of the 3T block.
i'm running megasquirt 2 -fuel only and road tuned by myself with the help of Innovate LC-1 WB o2. i still run stock ignition and run a locked 20BTDC ignition timing using NGK BPR7ES spark plugs. i still have problem with the setup as it miss firing badly at 5KRPM above. still yet to find out what is the cause.

[WDE_BDY]

The whole point of the CT26 off the 7M-GTE is that it is a virtual bolt on swap from the days when it was hard and expensive to find a good turbo. If you want cheap and easy its the way to go, for best results you might as well get a manifold made and get a more suitable turbo.

Callum

[o_man_ra23]

Your timing is the problem. The MS2 will directly fire a coil, so get the guts from a 22RE dizzy (or 21RC dizzy), put that in so you have a reluctor feedback to the ECU, lock the dizzy at 0 degrees and let the MegaSquirt work out your ignition timing. You need to RETARD the timing on boost (down to probably 5 degrees BTDC... this will depend on your setup and boost levels) and advance it on vacuum, up to a maximum of 33 degrees BTDC.

So go back, set up your ignition properly, tune that, then come back and let me know how much better it is.

[CHB]

so you means that static ignition timing just don't work?

[chris davey]

yes. if you are running 20deg timing all the time when you hit peak torque and whatever boost level it is likely that the engine will knock and could potentially die. Do what owen said

You shouldn't have to drop it to 5deg on boost though especially if it is a low comp setup. depends on fuel used also. When it is reduced to about 12deg, whatever boost level that is should be your maximum. You will need knock detection device to tune ignition timing. Fuel is the easy part.

BTW how is your friends car coping with boost if it is using an n/a ecu? it wouldn't be retarding timing either and I have no idea how it would know how much fuel to inject as I would think the map/afm would only sense to 0psi.

[o_man_ra23]

AFM is pressure indifferent, and only goes on flow, so it can work, but as you said, the ignition timing wont retard and it will detonate.

[CHB]

ok here is his combination(what i've being told). 4AGZE running a late model MAP 4AGE ECU, then he drop the fuel pressure to about 20psi(this is pretty nuts if you think of how the spray pattern will be). for the moment he only boosting 10-12psi and runs very well.. it sure run rich based on the spark plug readings. weird thing is that he fouled the spark plug even if he idle it for quite sometimes..

[o_man_ra23]

Sounds like a grenade with the pin pulled to me... dont drive along side him or you may cop a conrod in the side of your car