GTSi Throttle body is So Small

Its been done.

Doesn't make much difference.

Eight big throttles looks really cool but you still have only one cylinder per bank on intake stroke at any given time anyway so that one throttle feeds two at a time pretty well.

The lack of power had more to do with mild cams, low compression, EGR and very meek ignition timing advance curves, not to mention a great big restriction, a shock absorber really if you will, called an air flow meter placed upstream of the throttle. If there is any impediment to flow, it is there.

I am afraid you are just trying to reinvent the wheel.

If you really want horsepower start by drop kicking the CIS into the nearest dumpster and going with an electronic system. No matter what you do CIS will not accept cams that can make HP.

 

As Brian has already mentioned the downside of having the CIS system is the lack of HP over the earlier carburettor cars.The upside however is that they make an excellent candidate for supecharging though.

 

30+ hp gains have been reported by just eliminating the K-jet fuel distributor with it's restrictive metering plate with electronic injection & keeping the stock throttle body.

EFI & a modern electronic ignition will also help you deal with the emissions issue.

If you're making your own replacement plenum & risers & going with EFI, then you might as well use a throttle body for something like a Mustang. If you're just getting a stock plenum & risers, then I'd start with a stock throttle body with a cone shaped airfilter in front of it.

You might find this EFI conversion site relevant:
http://www.employees.org/~fty/efi/3x8QV_EFI_retrofit.html

The next big gain is to have the heads ported.

 

Who can properly port a 308 head (specifically a QV) without ruining it?

In other words, who has done it before and proved it on a dyno? I have been thinking about this for some time. Problem is it is a tricky business. You can't just hog one out. I need to find a shop that has been down this very specific road many times.

 

I would talk to Carobu and Norwood's. The measured increase in peak flow on mine was like from 94 to 109 cfm.

I could talk about my experience, but I would not recommend the guy that did mine as it took almost a year. You will also hear James at Norwood's say that it may not be worth the expense. For me, I had to find out. So on the dyno, I picked up about 25 or so hp from porting, perhaps more now that it is jetted correctly. Mark E. swears I could have picked up way more with EFI, and it will be interesting to see his final numbers. I think a hotter cam would have helped breathing at higher rpm, but I went for torque so the power comes in in the stock powerband which is what I wanted for a 3500# car. I'll emphasize that it is another case where it is best if everyting fits to what you want your engine to do, so set your goals out from the beginning. Our goal was a reliable safe and streetable 100 hp/liter. That's about what I have, and it really feels it.

 

For those who missed some of the early throttle body discussions, here are a few I found reviewing the subject today:

http://www.ferrarichat.com/forum/showthread.php?t=35078&highlight=kermit+throttle+body

http://www.ferrarichat.com/forum/showthread.php?t=88743&highlight=kermit+throttle+body

http://www.ferrarichat.com/forum/showthread.php?t=86905&highlight=kermit+throttle+body

Also to address why some folks seem a bit apprehensive about porting Ferrari heads, and not without cause, there was a well publicized episode by an FChatter that had his heads ported and broke into the water jacket. I do not think this is as much of a problem in reality as it is the only time I have heard of it.
WARNING: This historic thread is not for the faint hearted:
http://ferrarichat.com/forum/showthread.php?t=50989&pp=20&page=5

 

Did you see that tiny TIG torch Wil loaned Mark E in the V12 conversion thread? ..... very very cool!!!

Cheers

 

Have you checked out Paeco Industries in Birmingham that does a lot of exotic engine work? They should be able to handle what ever you throw their way.

Ciao,
George

 

In the olden days (early 1980s) Paeco had a mixed reputation, but a glorious catalog when I lived in Bham. Perhaps it is different now.

 

FWIW, I have been running a 90mm TB for quite a few years. Coupled with EFI and an near open exhaust, the car run great, especially in the upper RPM ranges.

 

That sounds really interesting! Are there any engine photos or dynos available?
Any comment on plenum modifications to accept the 90mm TB?

 

I have a little bit of TB fiasco going on and I have an extra one that I bored out to 2.7" from 2.6" diameter. Already made the new butterfly but there's a couple other things I need to do if I want to use it:

Bore plenum to match

New shaft bushings ... .010" clearance on this one which seems like way more than the one that's on/off my car right now.

Anyone think the extra area will do anything? The math say 8%. I know you posted links Russ how big did Kermit go? I need to get to work.

Cheers,

Sean

 

Kermit was very deliberate and measured, and IIRC he went from the stock 65mm or so to around 70 - about what you are doing. The 'attention to detail' items include mating the larger TB to the plenum, getting rid of the gosh awful flex hose for something smooth, and port matching the runners, mildly porting and polishing them. And, cleaning out the and polishing the plenum.

I do think you will see an increase; perhaps not 8%, but something measurable. He always was good about posting dynos and head flow numbers unlike many developers (although some took him to task). There are some numbers back in the archives somewhere, but I would bet it is not for the TB alone.

Something I see advertised for K-jet stuff and similar in the Porsche magazine 'Excellence' is the "Extrude-Hone" guy that bead blasts the interior of induction systems.

Good luck, post photos, and let us know how it works!

 

Note that plenum has been enlarged by about a 1 ".
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Wow - that's pretty impressive piece of handywork, there!
Any dynos or A/F graphs?

 

I can not find the actual dyno runs, but did find the A/F notes: Min: 12.1, Max: 13.5, Ave: 13.0. About 210 RWHP if I remember correctly. Very hot day with outside Dyno. As I said before, you really feel the car take off after 5K RPMS. I have it redlined at 7700, but it feels like it want to pull far past that point.

 

Paul, what is the cost for a project like this? If you don't mind me asking.

Thank you,
Anthony

 

The conversion was initially done by a PO. When I got my hands on the car, it did not run so I installed the Electromotive TEC3, wiring, new injectors, exhaust - about $2500 plus 100 hours. My gut tells me that simply installing a bigger TB will not buy you much and possibly nothing. Getting the engine to breath in and out is what's important.

 

Thanks.
I was thinking of doing a carb conversion with carb cams on my 1980 GTS. I already have the carb intakes. Just checking to see what kind of other options i have.

Anthony

 

This is the motor that's in my car ... a "cheap" EFI conversion as they go ... made 210 rwhp with 12:1 compression and the stock injection cams. She really pulls and I think there's a few more pretty easy tweaks I can play with to get some more out of 'er.

I'm working on several other itterations right now .... one motor with carb cams and the stock intake/throttle body ... one with the motorcycle independent throttle bodies and .380" lift intake cams .

I have a set of the carb intakes and thought about playing with the TWM setup ... a bit pricey though compared to the cost of the above.


Cheers,

Sean
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If there was any way to place the air flow meter so it was right next to the throttle body, do you thing that would help matters any?

Ciao,
George

 

You could put it anywhere you want, won't make any difference to horsepower. It existence is the problem, not where it is located.

 

The problem more exactly is the huge barn door air mass sensor plate that the air has to move controlling the fuel distributor - the usual convoluted and long path the air has to go is also a problem, but the air sensor plate is the restriction that a na engine has to suck around to breathe.