I know with bolt ons you really don't need a larger TB(at least that's what most people think), but what about with my mods?(sig)

John

 

I wondered the same thing about mine. Someone told me though, that bigger injectors are a better mod for our set up than a larger throttle body. Im not for sure though. Anyone else got any opinions?

Benji

 

I hadn't even thought about bigger injectors. I plugged in a laptop to the car the other day and it was pretty much maxed out rich. I'm not sure if I'm flowing enough air to need bigger injectors or not. I guess I really need to dyno with a wideband.

John

 

I personally think a larger TB might help in your case.
Some people are like " not worth the money, blah blah"
I think that with a cam and a little head work you should consider a larger TB a must. I would not go monoblade or nothin but a nice step up would help I think.
Keep in mind my engine is internally stock and I have not changed anything that would require a bigger TB but More air in = more power out.
I will do it when I go with my head and cam package no matter what anyone says.

 

John,

I'm running into this exact same situation. I had a 52mm before with the GTP Stage 1 heads and CC304. Now with the XE 224/230 cam and fully ported heads I think I need more TB.

Went to the track last tuesday and ran 8.28 @ 85/12.96 @ 105. But the MAP read as low as 91kPa at WOT and the MAF showed 261 grams/sec. That's low. The MAP reading shows a pretty big restriction/vacuum when the MAP should read 100kPa (atmospheric pressure) at WOT. I'm thinking I was down as much as 34hp with that condition.

Plus my 24lb SVO injectors were running at 92% duty cycle. I'm pretty sure once I get the airflow situation fixed the injectors are going to be too small. I have a BBK 58mm TB and SVO 30# injectors coming this week, then I'll hit the track and check the MAF and MAP readings plus track times for improvement.

What I'd recommend is do some logging/scanning of the PCM. Watch the MAP readings at higher rpms at WOT. If its less than 98kPa then you are probably getting some restriction. Its not always the TB but it can be anything in the intake tract.

That's how I'd approach it anyway.

In addition to all that above I'm still tuning the WOT fueling and shift points, but I suspect I can knock .3 or more off it it.

I'm pretty sure you need at least a 52mm. 58? I dunno, but if you're running heads/cam/headers and the stock TB you are probably losing some potential HP. I'm trying to sell my 52mm right now.

 

id get bigger injectors first.............having enough fuel is most important.


if you bother getting a bigger TB.......there was a thread in the "advanced tech" section awhile about about the benefits...........after reading that id probably get a 52mm if it was cheap.

 

Only way to know if you need more injector is to scan pulsewidths near redline at WOT. You have to look at the TB and injectors together as one issue, because if the injectors are running at 92% now and you decide that's enough injector, but then adding a bigger TB moves the MAF reading from 260g/s to 290g/s then that means you're going to need 11% more fuel which would put the injectors at 103%, meaning they are maxxed out and you need more injector.

Start by getting some baselines in terms of peak injector pulse width, MAP reading at high RPM right before a gear shift, and MAF grams/sec at the same RPM point.

 

How is the test and tune at BB on tuesdays? I want to get up there and run because the car seems to like BB a lot better than the hill. Comparing 1/8 mile times I usually pick up a solid .2 at BB over the hill, given similar conditions.

Anyhoo, the only thing I have to scan with is the free program from www.carputing.com It's not the best but I can get most of the info out of it that I need, I think. I'll have to go back and see exactly what it displays. Any ideas on where I can get a better scan tool, for free? I don't want to pay for one, because I don't own the cable I'm using, it's just borrowed.

John

 

The Tuesday TNT was good...NOBODY there...maybe 15 cars. It was just incredibly hot.

The best OBD1 scan tool is Datamaster by TTS. Its free to download and you can use it like 30 times before the free trial locks you out. I think the website is ttspowersystems.com, might have to do a search for it.

Let me know what your #'s are on those three items after you get some scans done. This time next week I should have the new stuff on my car and I'll let you know how much the airflow increased and if the MAP readings improved.

My MAP was fine (99-100kPa) until 5400 rpm, then it started dropping until 6000 rpm where it was 91-92. That's an almost 10% vacuum. Theoretically I'm giving up about 35hp because of that.

 

Found it-

http://www.ttspowersystems.com/DM_Software.htm

I'll let you know what I find.

It was hot at the hill too friday, but I managed a 8.5X with a 1.94 sixty foot on the stock tune. I got my tune from PCMforless in the other day and it feels a lot better now. I actually have some low end and no stumbling. The car was running so rich that when I hit the gas it would backfire and then take off. I'd like to eventually get into tuning the car myself, but I have a lot of research to do and also need some more money to get the software and cable. But I'll be back at the hill tuesday to get some new times with the tune.

John