I used to believe that too because.... Because i read it in books. Lol. But in practice, with the cars all coming stock with SRT turbos ( small retarded turbos), its would be really hard to get " too big".
My first couple turbo cars had reasonable size coolers, and despite the obvious, I figured the were good sized. Then... Then came the srt4. I did a cyborg type upgrade ( we basically pioneered what hundreds and hundreds of srt4 owners have done with the stock turbos. We did all the R&D, then 2 years later 4-5 different shops had copied us and did the same turbo, we called it "SST" super stock turbo). Anyway... Did the SST, hit it with 100shot of nitrous, and obsessed about all the tiny details i could "tune". When I finally saved up my $385 for a ebay srt4 intercooler, I second guessed it for the same reason. All those books written 20 years ago by some really smart guys ( most will reference Corky Bell when this comes up ). But... My charge temps were 250-260 degrees coming out of the intercooler and that just seemed high ( comparred to our fist, its batshit crazy high ). So I made the leak because "race car". At the time ebay intercoolers were thought to be total, un-usable crap. The AGP build option that was the closest was $600-$700. I'd never have saved that much. So... I installed the ebay cooler. It was 24x12x4". Back then... That was "way too big" for a td04 turbo with a 15G wheel.
I still did it.
My first impressions were "holy crap, not only is there not more lag, but the car drives WAY WAY better off boost, rowing through the gears". Then the charge temps... Most the time, they stay'd down around 120-125 degrees. The power increase from the cooler charge temps was crazy. Power was likely increased by the ecu letting it run more timing as well. But wow... It was the second best mod I ever did to the car. There was ZERO difference in lag. There was better throttle response off boost. And the car made way way more power, and it did it more consistently. After meth injection, I could get BELOW ambient temps, but that's another story.
Later... The srt4 guys did some testing. All on the same day, they swapped intercoolers out at a dyno day on two different cars.
What they found was... The ebay giant intercooler actually made MORE power than a spearco costing $800, on a stock turbo srt4, while the spearco was actually a bit smaller. The ebay intercooler also matched the $600-$700 AGP equally sized cooler by like 1-5hp on the stock turbo. Proving... The bigger intercooler on an extremely under sized turbo is the right way to go.
The catch was.... When the coolers were swapped to a car with a AGP garrett 50-trim turbo kit, the ebay cooler DID NOT flow as well. It had a better cooling capacity, but the Spearco actually beat it by a reasonable amount at like 400whp on a big turbo car. They concluded that the extremely hot air coming off the stock turbo was flowing through the spearco SO FAST that it did not get time to transfer enough heat before passing into the engine. The more restrictive ebay cooler held the air back longer and cooled it, coupled with its larger metal mass to dissipate heat.
So now after living it and having experience, I never under-estimate the difference an "over-sized" intercooler can make on a small, stock, heat spitting turbo. If I didn't have that experience, and lived/tested it, I may have been fully agreeing with you "the Duke".
As far as Corky Bell and all that, I think that ole Corky never envisioned at the time of his writing of his book, that we would have peanut sized turbochargers cranked to 25psi on ford fiestas, lol. I think on that topic, he's more thinking a buick grand national or small block chevy V8 with at least close to properly sized turbos, not turbos that make 29psi at 2870rpm and run out of steam at 4800rpms, lol.
Its no wonder that pumaspeed has like 3 different options for intercoolers that are "bigger", "quiet a bit bigger", and "way bigger" than an of the currently available intercoolers we have for USDM cars.
Our cars are super sensitive to charge temp too. You can see the setting in race tuner software (cobb). So not only will you lose power via warmer air, but the ecu dials out timing as well. Its a double edge sword, and that's why its #2 on my list.
I think i just set the record for off topic rambling, but whatever, I'm bored and wanted to share, lol.
Stock
$385 ebay one i had
$800 spearco
AGP Race ( Inthink they updated it)
