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Gotchas & Tips
Sluggish in hot weather Useless mods 2JZ-GTE specific tips C20LET specific tips
It is my opinion that clowns work best in circuses, because that is the environment they were meant to be in. Unfortunately, some have broken ranks and decided to operate in the turbo-reconditioning business. Not a funny prospect. Make sure that you get a couple of recommendations from people you trust, or else you might end up with the jokers that damaged my own turbo. Sending the turbo to a 'well known' firm (maybe even with a website!) is a straightforward job. But the quality of these 'recons' varies enormously. Lots of people end up sending their turbos back and forth, only to realise that every time they smoke or leak worse than before.
Here is my story: I sent it to a reputable establishment by all appearances. The turbo was back within a week, looking like new. I was well happy with the results, but held judgement until it was on the car and working properly.
...Which it never did. Right from the start there was the smell of burnt oil. I put that down to the various oily surfaces, quite normal after an engine rebuild. But the stink never went. I thought it was down to something dripping on the exhaust, so I tighten up all sump bolts etc, but to no avail. The stink was also in the cabin, so I investigated oil leaks in the engine bay that could end up through the ventilation system. Nothing. The stink was getting worse by the day, so I dismantled the exhaust looking for collapsed passages. Nothing. Then one day as I stopped at a junction I saw a smoke cloud overtaking me. I thought "there must be a banger behind me, surely!". There was noone.
From then onwards looking at the mirror I could see the smoke clouds during deceleration or light throttle. It was getting worse by the day - after 1000 miles the smoke was so dense that I decided to open up the head and change the valve seals, once again. No difference. I was just trying to find excuses not to blame the turbo.
The recon company very helpfully took the turbo back, and promptly blamed ME for knackering it (foreign material oil contamination, too low exhaust backpressure, too much crankcase pressure - you name it, they blamed it. They already had my credit card details, so they casually charged me for the second recon as well, and sent it back 'good as new'
Alas, it was leaking oil and smoke just as badly as the first time.
Then they sent a 'new' turbo, a recon of another core. Still crap. These people were hopeless, didn't know their arse from their elbow. But I needed hard proof.
So I sent the turbo to a competitor of theirs to see what they thought. Their assessment was very clear: in fact they originally thought that I had tried to do the work myself and I messed it up - it was that bad. The repair wasn't cheap, but now it works like clockwork (only faster).
After a long struggle with their moronic technicians and clever solicitors I managed to get my money back - without having to go to the courts. This is the reason why I won't mention names here - but the truth remains: the clowns are OUT THERE
White/blue exhaust smoke - help!
This is a common issue, and most people are quick to jump into the conclusion that the turbo needs reconditioning. Hold your horses, this is not necessarily the case!
There are four possibilities here
- The engine is producing the smoke
- The engine is forcing the turbo to produce smoke
- The turbo is smoking
- All of the above
1. The engine is producing the smoke
Valve stem seals on older engines can allow excess oil to enter the combustion chambers. This will manifest itself as exhaust smoke (smelling of burnt oil) during idle and deceleration mainly, but in reality the smoking will be constant. These symptoms are quite similar to those of a turbo bearing being out of spec. Changing these seals means taking the cylinder head off and dismantling the valves - not a bad thing to do on a high-mileage engine, anyway.
The piston rings could also be tired and loose, letting excessive 'blowby' go through the rings, pressurising the sump and getting out via the crankcase ventilation (thick pipe next to oil dipstick -> camcover sealed passages -> thick pipe at back of camcover -> turbo intake). This can be 'rectified' (read:: botched) by blocking off the small intake pipe at the turbo end, and venting the camcover pipe to the atmosphere via a small airfilter, and/or an oil catch tank. These blowby gases are poisonous and corrosive, so we don't want to breathe them if we can avoid it!
A compression test can show if the rings are in need of refurbishment (local copy here). Even if the figures are within the acceptable range, the rate of pressure build-up is a good indicator. While cranking the engine, fresh rings will show (say) 165-170-175-175-175psi. Tired rings would go like 155-165-167-169-170-171, building up pressure for several crank revolutions. A dry/wet test would also show a couple of bar increase during the wet cycle.
Even better, a leak-down test will show even more precisely if your rings are done. Local copy here.
Here's how to make a leakdown tester for minimum money
2. The engine is forcing the turbo to produce smoke
Blocked breather pipes would fall into this category. They could be full of oily and sticky residues becoming effectively blocked, or kinked. This would lead to the sump becoming pressurised, creating pressure that would not allow the turbo oil return to flow (it's gravity-run, remember, as opposed to the turbo oil-feed that's pressurised). Therefore fresh oil would be piling up through the oil feed, but with no easy exit, the oil will have to push itself back through the turbo seals finding itself both into the intake charge and directly to the exhaust gases. Fixing this blockage would correct the problem immediately.
For idle and very low throttle openings, the LET also has a smaller breather hose from the camcover to the bottom of the inlet manifold - via a flimsy one-way valve. This valve ensures that under boost the camcover isn't pressurised. It only helps suck out the crank fumes while off-boost.
3. The turbo is smoking
That's when the clearances within the turbo are out of spec and oil leaks through the seals whenever there is pressure differential. High-flow exhausts exacerbate this problem, as of course running high boost pressures.
There is this theory that 'thin' oil leaks through the seals while 'thick' oil doesn't. Conventional wisdom would support this argument, but I have seen no evidence whatsoever to back it up, despite changing from the thinnest of oils (synthetic 0w40) to the thicker ones (15w50).
4. All of the above
In real life, older engines would tend to suffer from all of the above, especially if they haven't been reconditioned in the past. So the head would be full of carbon deposits, the stem seals leaking, the turbo seals past their prime, and piston ring blowby on the high side. Trying to pinpoint the 'blue smoke' to just one factor can often be futile, as there are several contributors, and even fixing one of the causes would still leave the car smoking.
People come back from the Rolling Roads, excited and happy. They carry proof, a printout showing how their 100K mile old rustbucket gained 10bhp from a panel filter and new set of plugs (cold ones, of course, that's where the power lies!). Gained compared to what? one might dare ask. The manufacturer's figures, dummy - now how can we argue with that, eh?
Hold on - if the manufacturer claims 150bhp from a brand new example, how do you assume that you've lost nothing from your worn-out bores, carbonised valves, rattly exhaust, corroded electrics, half-blocked injectors, overstretched throttle cable, etc, etc...?
Rubbish - my car did 160bhp on the RR, and it's got a Hi-Flo panel filter, so it's gained 10bhp. Go away, you killjoy...
So what "Brake HorsePower" is that then? Flywheel?
Did anybody take your flywheel apart and attached a dyno to it? Probably not.
What you got were figures from a chassis dyno. This can only measure two things on it's rollers: revolutions and torque applied.
EVERYTHING else is calculated based on arbitrary 'correction' factors, questionable settings, dodgy calibration and ludicrous 'transmission loss' adjustments. If you want to be closer to the Truth, then ask for the 'power at the wheels' curves, without this bull added up. You'll get much lower figures, but you'll know where you stand. Then after you do a mod or two, go back to the same RR and get another 'power at the wheels' graph to compare.Hang on, are you saying that my RR operator cheated? Why would he do that? He doesn't know me, and he doesn't get paid by the bhp, either... No mate, there was no hanky-panky with my readings...they're pukka
First of all, you can't tell if you don't know what to look for. It's mainly settings and parameters that are set beforehand, so the 'fluff' is spread to everyone.
Incidentally, more powerful cars tend to get even more inflated figures, as the transmission losses 'compensation' gets totally out of hand. For example, on a tuned 800bhp car, I've seen the breakdown including 300bhp as transmission losses!
Also check the barometric and ambient temp 'corrections'.
An old trick is to stick the ambient temp sensor under the bonnet, or somewhere hot. The software then compensates for this insanely hot 'weather'. I've seen RR printouts with ludicrous ambient temps proudly displayed on the 'small print'.Here's an example. Look at the bottom right end. 52C in Central Scotland? Late September?
Not this side of the ice age...
Let's go back to these dyno graphs, because they were all done on the same car and the same garage. The first one shows the car (LET) in standard trim. The second one is when a (sub)standard chargecooler was fitted, and the third one is with the EDS FMIC.
Power at the wheels Drag (calculated) Power at the wheels corrected Adjusted to DIN standard (Final flywheel figure) Ambient temp We can see that with the FMIC the power at the wheels increased by 10.5%. This is consistent with reality. Even a bigger, thicker FMIC won't make more than 12% on a stock car - this I've checked myself. It's the law of diminishing returns as FMICs easily bring charge temps very close to ambient (on std boost).
Now the fun starts. For some reason, the FMIC resulted in a 12.3% increase in transmission drag! We can't even speculate that the gearbox and txbox oils were cold and solid, because ambient temp was entered as a preposterous 48C (That's Saudi Arabia temps during midday!)
The corrected power at the wheels has gone up by 11.11% - bit more than 10.5%, every little correction helps!
The final flywheel figure (adjusted DIN) went up by 17.2%
So how come the various adjustments resulted in a further (17.2-10.5) =6.7% power increase? In this case it's easy to spot: the fake 24C increase in ambient temp would be responsible for 5-6% correction (bit less than 1% power for every 4C). The rest is due to compensating for the (miraculously) increased transmission drag.
Isn't life beautiful?
You didn't answer my question: WHY would they do that, there's no motive
Ah, but there is: think about it: if the manufacturer claimed 200bhp for your pride and joy (which has seen better days, but let's no get into that now!) wouldn't you get depressed if the RR showed 180? Be honest now.
If there was another RR nearby, where your car would show 208bhp, wouldn't you ultimately stick to that garage? 208 is nice, because it's just over the manufacturer's figure and it implies that yours is a goodun, a Monday morning special, accidentally blueprinted, have your pick. Dodgy, but flattering. Keeps the punters happy. Victimless crime if you like...
Here's someone else who had similar experiences (local copy here)
More reasons to take RR results with a pinch of salt (local copy here)
Dynos don't lie (local copy here)
More dyno circus (local here)
Here is how dyno correction factors are meant to be (local copy here)
If however the RR doesn't give you the figures you want, (or feel you deserve!) there are various web-based Rolling-Road excuse generators - just do a search.
Here is the ACTUAL formula for SAE J1349:
SAE J1349 JUN90, converted to pressure in mb:
where: cf = the dyno correction factor
Pd = the pressure of the dry air, mb
Tc = ambient temperature, deg C
Sluggish performance in hot weather
It's not just yours, all turbo cars are affected by high ambient temperatures.
The inlet air temp is higher, meaning that the air is less dense - so the turbo has to work harder to compress this air and produce the required boost. But because the air is worked harder, it leaves the turbo hotter, so the intercooler has to do more work, yet it has less dense/cool air to exchange this hotter charge air into. A harder-working turbo compressor also risks getting outside the optimum efficiency range, heating up the charge even more. And when the intercooler does manage to shed some heat, it just ends up in the engine bay, preheating everything even more.
That's why turbo cars suffer a double whammy with regards to performance compared to normally aspirated engines.
Here is a list of totally useless modifications people feel compelled to spend their hard earned cash on. Some are simply cosmetic, with fake technical benefits promised.
The problem is that the downsides are not always obvious.
If you feel that spending money on such 'mods' enhances performance (or even your social status) then here is guide to turbocharging a Fiesta 1.1 (cheap, too)
2JZ-GTE specific gotchas and tips:
C20LET specific gotchas and tips:
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